Now that’s not something I’ve ever noticed before until I just took a listen to compare.
So, the real answer is because I used OOT audio for the scene due to removing audio-affecting things before, during, and right after it, and because I wasn’t aware of the difference. I suppose it could be understood as a delayed reaction due to the mind trick. Ben responds quickly as soon as the trooper finished parroting his last line.
I am glad you enjoyed the film overall this way, though. I’m looking forward to watching the hopefully-complete-by-then Hal9000 presentation of the 9-part saga next year.