I still don't get this MUFY-guaranteed placement in Monash if grades are met thing.

Fristly, how difficult is it to get into Monash normally? It's not Harvard. Are you in such a bad shape that you need something like this to make sure you get into a normal average university?
Secondly, if you're so scared that you won't do well in any other pre-u to get into Monash, so much so that you are choosing a program that explicitly guarantees placement at the provider school, you should be asking yourself if you could survive in university or more importantly, is going to university the right decision?