April 2020
2 things.
1. If you start a Finisher, you can no longer cancel out early. You're committed to doing it all the way through. Risk vs. Reward. This prevents the issue where you can start a finisher when someone has a KD shield up and then cancel it to quickly kill them before they can put the shield back up. The purpose of the KD shield is to force enemies while in a downed state to expend time either flanking you and killing you or breaking your shield to finish you. The Finisher bypasses this, but at a risk of getting killed. In the event the Finishing player is killed before the animation completes, the downed player is not killed.
2. Because Respawn loves to bind multiple functions to 1 key, either allow Finishers to be bound to a separate key or separate the functionality of the USE/REVIVE function from the initiator of the Finisher by making 1 press and the other hold. Otherwise downed enemies will crowd downed teammates and if you get locked into a Finisher when you need to pickup a teammate, this would be counter-productive.