Your points are both valid, thanks for genuine discussion.

I wonder whether people marry similarly aged folks because of their ages or because of other confounding factors. Like everyone being single and unmarried in early 20s, a lot of people marry friends or suchlike that they knew from highschool that kind of thing. Also cultural acceptance cannot be overlooked. People might not enter relationships with people 20 years younger than them like this purely because it's socially frowned upon, as shown ITT. That has nothing to do with either person and everything to do with society.

Maturity would contribute to a more stable personality but that doesn't necessarily equate to a better personality or one that is incompatible.

Guess it's moot because it's rare but I would say that it's rare for a lot of other reasons than just two people who are 30-50 being incompatible. Not to say that they wouldn't be, just a lot of factors involved.