I believe this is more about reaching the full potential that regular complete nutrition and not living economically precariously enable I think. Pretty sure that’s me and my fellow whites are (generally) so much taller than our not so distant ancestors at least.

edit: Also, the uplift of people out of poverty in the 90s was still ongoing, I’m just not confident enough to speak with authority on it. In any case I don’t think it would account for the dramatic on-going line go up effect here.