Yes, although I agree with you that, in theory, there could potentially be an issue, I think the chances of this set of circumstances happening (i.e. someone marks or knows of a marked card, AND can recognize it, AND the one above just happens to be the one that gets exposed, AND it is not one of the first two cards, AND the mark happens to be clearly visible after the replacement card is dealt, AND the person who knows the card remains in the hand....) is probably so small practically speaking that it would be overkill to change the entire rule just for that. But I do respect the fact that you've put your mind to the risks.