First, this issue of teachers discouraging students from taking "big, flying ukemi". I still don't get it. I CAN understand the reason behind, but sometimes I just have the urge to have fun and get myself thrown hard, and do everything very dynamically even if the style sucks. Teacher says this is not the objective. The objective is for uke to feel what tori is up to and to follow the lead. So if you throw yourself into a breathtaking, magnificent neko ukemi whereas tori intended to let you down at his feet and apply a lock, it's simply bad aikido. I recognise that I'm still not at that level where I can recognise tori's intention, and I'm still too much occupied to push through my own movements.
I remember Saito-sensei saying somewhere that real Aikido doesn't give a chance for uke to do ukemi. Second is my opinion that uke should always be attacking where he has the opportunity, even when nage is trying to pin him down.
Doing big, flying ukemis either says that uke jumps for safety reasons (nage jerks the technique) which in this case is understandable and justifiable or he has totally submitted without even trying to regain composure and attack again. The 2nd to me is bad aikido. It's just for pure show.