Well, in Multiplayer this is something that makes sense since you can't have everyone be frozen just because one person is talking. Also the ability to distract an NPC with conversation while another character sneaks up on them to attack/steal is fair game.
The reason it stays in single player is because if it didn't then multiplayer would have even more obvious advantages than it already does.
As has been pointed out you can still get caught sneaking and anything you do the system can respond to separately.
Not an exploit. Intended feature.
