In the other hand, uke is conditioned mentally, that it is safe way to receive a technique. But in reality, it is a true only in Ch.Tissier style. Many styles will not allow such liberty for uke - and for a right reason - from martial point of view such liberty WILL be used by uke against nage.
So such fancy flips become very dangerous for uke, he stops to listen and feel nage's body and can be badly hurt.Doing high flying flip uke can't adapt his position if nage decide to change a technique.
That has happened to me once. We don't usually do flips with anything and one of the few things we do it for is when someone does kotegaeshi to the side and much faster than usual. So one day I was experimenting a bit as my friend practiced kotegaeshi on me and I flipped to receive the technique. Instead of letting me land, my friend changed the technique mid-throw and pulled me in the other direction. I was lucky I still landed on my shoulders and back. Then I got a scoulding for doing that with normal kotegaishi..