(It makes some intuitive sense to me... there are really old people and really tall people, but when's the last time you saw a really old really tall person?)
Even ignoring all possible cohort effects (e.g. people growing up in the 1930s getting worse nutrition than people growing up in the 1990s), that just sounds like Berkson's paradox.
(I have no objection to the rest of the comment, and indeed I upvoted it.)
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.