From what I can tell, it seems like Criterion had more trophies planned, but simply ran out of their alloted points and instead of redesigning the trophy list, they left it as is. The lack of a gold trophy for smashing all gates and billboards is what gives me that hint. Needing only the first 50, minus the platinum itself, trophies also adds to that feeling.
It's strange that it doesn't require the trophies for the Cagney and Bikes updates since anyone that can go online to get the trophy patch will also have the ther updates, as well, so it's not much of an issue of those people not having them.