The tracking on the activity card won't show the correct number. Instead, the trophy now unlocks when it sees you having 100% in-game. Mine unlocked and I was at 596/603, yet in-game everything needed was at 100%
This is also on a save with the missing moth and flying book in Hogwarts (as they don't actually count towards the collection) - this new update didn't make them appear, yet it didn't matter. Also, my save didn't have the PS exclusive mission as it never appeared and I can't get it to start - again, this didn't affect the platinum unlocking though.