This will be clearer in next verse:

Bg 5.5

yat sāṅkhyaiḥ prāpyate sthānaṁ
tad yogair api gamyate
ekaṁ sāṅkhyaṁ ca yogaṁ ca
yaḥ paśyati sa paśyati

Word for word: 

yat — what; sāṅkhyaiḥ — by means of Sāṅkhya philosophy; prāpyate — is achieved; sthānam — place; tat — that; yogaiḥ — by devotional service; api — also; gamyate — one can attain; ekam — one; sāṅkhyam — analytical study; ca — and; yogam — action in devotion; ca — and; yaḥ — one who; paśyati — sees; saḥ — he; paśyati — actually sees.

Translation: 

One who knows that the position reached by means of analytical study can also be attained by devotional service, and who therefore sees analytical study and devotional service to be on the same level, sees things as they are.

yat sāṅkhyaiḥ => That which is obtained by Sankhya or obtained by Karma sanyas. 

prāpyate sthānaṁ -> the destination that is obtained  

tad yogair api gamyate -> That is obtained by practiced of yoga also 

understanding this 

ekaṁ sāṅkhyaṁ ca yogaṁ ca -> when one sees Sankhya and yoga both to be equal. 

yaḥ paśyati -> one who sees like this 

sa paśyati -> one who sees thus is the actual seer, one who can see.

 

So there is diversity in paths but there is uniformity in goal, now these verses in no way support the idea that all path leads to the same goal, Shri Krishna is talking about two specific paths over here the path of intellectual retrospection in inaction (inaction based on jayan yoga) and path of action based on karma yoga. Both these two leads to the same goal not that all paths lead to the same goal. That is not the teaching of BG or scriptural teaching this is also not logical teaching, this is already discussed in 4.1, here Shri Krishna is talking something different He is taking two specific paths and goal of both these paths is to ultimately free us from bondage and He is saying both these path can free us from bondage but the vital point is when they will free us from bondage? When they are done with detachment. So whether one has authentic detachment and renounces the world, renouncing all the activity and renouncing all involvement with the world Or one has detachment and one lives and acts in the world, if one has detachment in both cases one will attain freedom from bondage but detachment while doing activity is easier to do (as doing activity is natural to us ) than detachment while giving up the activity as giving up activity is unnatural so here Shri Krishna is not talking about the differences He has already said that Karma yoga is better now He is saying both of them are same, both of them ultimately leads to the same goal, the destination obtained by sankhya is same as destination obtained by yoga and therefore ekaṁ sāṅkhyaṁ ca yogaṁ ca.

 

So now how does it works out that both leads to the same destination? Normally there is hierarchy there is (1) (lowest) karma Yoga (2) (higher) there is Gyana yoga and (3) (highest) there is Bhakti Yoga.

 

So when Gyana Yoga is higher why is Shri Krishna saying two are not different? How are they ekam because of both are meant for same goal so karma yogi is also living for liberation and Gyana Yogi is also living for liberation and by practicing anyone one can attain liberation. So in terms of goal Karma Yoga and Gyana yoga is similar. 

 

In 3rd chapter (spiral curve) Shri Krishna said you practice karma Yoga because you are qualified for that and if you think that you are qualified for Gyana yoga still you practice karma yoga as you will set good example for others by it, there Krishna has allowed the notion that gyana Yoga is higher than Karma Yoga but then He was saying do not practice gyana yoga it, it may be higher but don’t practice it by practicing you will become Mithya chari but here Krishna is taking the discussion on higher level by saying actually Gyana Yoga is not higher in once sense in yoga ladder it may be higher but it is not that Gyana Yoga will lead to higher destination, ultimately whatever is meant to achieve by gyana yoga same will be achieved by karma yoga, by both liberation will be achieved. So ekaṁ sāṅkhyaṁ ca yogaṁ ca, the person who see both as same is the true seer. 

yaḥ paśyati sa paśyati indicated a deeper meaning -> one who sees like this is true seer. So here Krishna is talking about seeing with knowledge. E.g. a chest X-ray shown to a layman and a Doctor -> it is seeing same thing but lay man doesn’t see what a doctor can see. So we see with knowledge. We see with the preexisting understanding we have, so what we can know depends on what we know. So whatever we hear depends on what we know then only we will be able to connect. So what we can know depends upon what we know, when I look at x-ray I cannot understand but a doctor understand it quickly. 

Just quoting standalone verses doesn’t indicated deep understanding of BG. All this indicate is some  piousness by memorising BG verses so we need to study it more systematically.

 

So a person not doing anything, contemplating and grave we may feel he is more advance than a person engaged in all kind of activity in karma-yoga but it is not so as destination is same.

Srila Prabhupada: The real purpose of philosophical research is to find the ultimate goal of life.

 

So what is ultimate goal, Prahllad Maharaj says in 7th canto that people doesn’t know that ultimate goal is to know, serve and love Lord Vishnu.

 

Srimad Bhagavatam establishes that Sri Krishna is the absolute truth, supreme personality of Godhead but after that Bhagavatam used the name Sri Krishna and Vishnu identical and inter-changeable. Even in the Rasa Lila pastime where there in no Vishnu it says that who hears this pastime of Lord Vishnu…Philosophical point makes it very clear that Krishnas tu Bhagvan swayam but after that it doesn’t go into hair spitting analysis it simply focuses on the point that Krishna and Vishnu names are identical and inter-changeable .

 

Someone after digging the root is watering the root, but someone has faith and if he has heard from authority he will start watering the root without digging it. So in both ways if someone will water the tree the tree will nourish but second process is easier, similarly Karma Yoga is easier. 

So body is like tree and soul is like root, so even if someone come to know after sankhya that he is soul ultimately he has to water the root, perform devotional service, so even someone from beginning practices bhakti yoga it is same.

 

Srila Prabhupada: although superficially one process appears to involve detachment and the other process appears to involve attachment. Detachment from matter (Gyana yoga) and attachment to Kṛṣṇa (Bhakti Yoga) are one and the same. One who can see this sees things as they are.

 

Attachment to spirit in general is Karma Yoga.