Depot doesn't have to be 17AA, sinse it gets released into blood slowly, peice by peice, and it's get broken down fairly quickly also,comparing to any 17AA oral, but still effective, because of slow release.
In case of tabs, whatever he takes will enter liver very fast and will get destroyed almost immediately. Acetate ester is useless, because it's not Depot but oral.
I was wrong saying that ester protect while passing through liver and I edited it already.