Division by powers of 1000 ceased to be an expensive operation relative to user interaction a very very long time ago. And even back when it was, I am sure would the error have been in the order of 10% (as it is now with TB vs TiB), they absolutely would have taken the more expensive but more correct operation.
I just see no advantage in continuing to resist the unification of the meaning of prefixes. And where people prefer the old way for some nostalgic reason, just put the 'i' in there and you are good.