A interesting comment from a YouTube user gianni737:
The reason Prince is being weird and Michael is so much more polished here is that it’s August/September 1983. Prince’s first big shows had only been a few years previously. He was in the middle of recording tracks for Purple Rain at the time of this concert, and shooting for the film hadn’t even begun yet, so he had not yet become a legend. Michael already had 15 years of regimented recording and performing experience behind him, so it’s natural that he knows what to do and appears so polished.
Thanks Jason, and Vic for reminding this existed.