Thats really interesting about the failing to go solo Reverserbucket I'd never really thought about critical points in flight training before, I was thinking up until now what a waste my PPL was (years ago) since I'm on an integrated course now but at least I know I have the capability I suppose.
I would think then the other points would be the instructor check before solo nav and maybe a bit of instrument stuff in terms of co-ordination etc? I wouldn't think CPL test as I have never seen a school anywhere which will send you to test before you are ready and most failures I know are nerves/brain slips.