Well as far as I can tell he's only talking about it retaining the matches from the last if/$iif(), meaning it's hardly going to be a large amount to store.
cold: $ifmatch would naturally be kept for backwards compatability anyway. Even if it was slower using $ifmatch() I don't think it would have any impact on $ifmatch. I'd imagine they're treated separately (based on the fact that you can create and use aliases with the same name as built-in identifiers provided they don't take parameters if the built-in one does and vice-versa).
