[basing this question on the Falcon 9, Paz satellite launch on 22 Feb]
Hi, this is probably a silly question, but there is an approx 3 minute time difference between second stage engine cutoff and the payload deployment stage. Why is this needed?
Three things happen in sequence at the end of the final burn:
What's needed in pre-release varies. You want the satellites attitude control to be working when you release it, but there are some things (opening pre-valves, etc) that you don't want to do while the satellite is under acceleration. But generally, this entire sequence is just a couple minutes of work.