here's a video kinda explains the upshift RPM holding:
Sometimes If i'm driving lets say 4th gear, and I wanna rev at a friend of mine who's driving next to me, all I do is clutch in ---> full rev---> still clutched in -----> RPM slowly drops and STOPS at the desired rpm for 4th gear ----> it'll stay there for a good 2 seconds before it drops it beyond that point. then I quickly let the clutch go. No jerk.