Herc pulling Manhattan wasn't a falsehood when it happened and it hasn't been determined to be a falsehood in any story since. The only leg you have to stand on is a sentence from an editor in an obscure index. Assuming that is the case, the feat needs to be retconned out of cannon in a better manner than that. Preferably on panel.
Marvel No-Prize book, which specifically listed blunders and errors in past stories:
That "on panel" enough for you?