Changing Who Learns What...

I think it does teach Sabin all of his Blitz's due to him not naturally being able to learn Bum Rush before the others level-wise. Even in the Editor, if you set Bum Rush to an earlier level than say... Suplex, he won't learn it before gaining all the ones that come before it in the list. So, the game should give you all the missing Blitz's when Duncan teaches Bum Rush at the same time.