I had watched the Chris Rock debut before but missed a couple things that you two talked about. I wonder if Chris Rock was supposed to do five originally but he came in too hot for the show so they cut him off. That would explain the confused looks but Rivers still bringing him over.
So I did some more diving on the clip, apparently it was the last episode of the show. So it very well could be that they were running short on time just because of all the closing segments they were probably trying to fit in.