...what does any of this have to do with the fact that an increase of die size by 1 is a +1 bonus on average? i don't care what the chances are of rolling above a 5. that's not relevant. 2d6 and 1d12 aren't relevant either because we're talking about versatile weapons. what's even your point?
my point is that, as a property, the only thing heavy really indicates is that small creatures can't use it effectively (and i guess also that it has certain interactions with features but a number of those also interact with two-handed anyway). i find it boring and lazy and, considering that halfling can get 20 strength and eventually pound down gods with a longsword, kind of arbitrary. hell, honestly, i'd prefer if they gave small creatures lower strength maximums or something, because that'd at least be a bit more interesting.
in other words, i don't really have that much of a problem with restricting what weapons smaller creatures can use effectively...i just think the heavy property is the most boring way to do it.