OK, so it happened that Pius XII just got tongue-tied and got two sentences mixed up in his head and inadvertently asserted the "not". So clearly manifest MATERIAL heresy no longer suffices to effect deposition. You also correctly anticipated the next step by saying that he has to be given the opportunity to recant. In other words, even if Pius XII intended to utter a statement (wasn't just tongue-tied), let's say it was something that he didn't KNOW was heretical and immediately retracted when someone pointed out to him. He would have been guilty of only MATERIAL heresy.
So we moved very quickly from MANIFEST HERESY deposes ipso facto to MANIFEST FORMAL HERESY. We've already added another adjective / qualifier.