In previous versions (tested 1.20.4), when entering an end gateway, the player's velocity would be reset, meaning jumping horizontally into an end gateway would safely place the player with zero velocity at the exact-teleport exit position. In Minecraft 1.21.4 (and presumably since the large-scale teleportation refactors), the player's velocity is reset.

As this was not mentioned on changelogs to my knowledge, I believe this regression to be a valid bug.