Karate: Enpi Kata, known as the Swallow Kata, can anyone explain why the JKA removed the hand motion after the rising punch?

Empi means to fly like a swallow, Its a representation of the quickness of the movement, shifting and turns.

I learned a few different version of the kata over the years, the techniques you are referring to can have a number of interpretations. The one I use the most for the raising punch is a strike just past the elbow of the arm, then grabbing the arm and pulling the person in as you move forward to the next movement. I have seen others where you are striking under the jaw and then reaching around the head or grabbing the hair.

As for the jka why they removed it, I suspect it has to do with them wanting karate to be a striking art and not an art with both. The interpretation could easily be a strike under the jaw and then a finger thrust into the throat. At least that would be mine the jka may have some other purpose. Personally I never liked there interpretations. They are very limited in their bunkai.

Can you provide a video reference of the kata with the hand motion. We don't do Empi or it goes by a different name in our system.

I can't say why JKA removed anything. Other than them removing the grappling out for competitions. In the many different styles of karate many share the same kata with slight variations. It can be to make it different. It could have been because the person that introduced it to a different group was teaching it wrong. It could be because of a different viewpoint. There are many variable as to why a kata is the same kata is done slightly different in different schools or systems.

Edit:

I'd imagine that the move your are talking about is the one at 2:13 in Kokoro video and about :45 in your video. I don't recall doing this in matsubayashi ryu. But I'd imagine it can be a variety of things. Liek Kokoro said a upper cut. But I see more of an elbow strike after grabbing the head. I see a throw (ippon seo nagi). I also see a standing choke.

How should we know why they modified the Kata? All I can tell you is all positions, movements, and even the bow in method in any Kata can be interpreted as being something useful. That is to say the hidden application of any position, stance, kick, hand technique, turn,....etc all have multiple actual real life applications. If the JKA changed something then they also changed the associated hidden meaning/application.

No sense what they did.