AZ, I’m wondering who in the MO community you are talking to. Because for the last 10 years or so, most of the couples I know are within 2 years of each other. Many the same age.
A few reason:
1) A lot of couples start dating in high school. You generally date within your age range in high school (so 0-2 years, 3 at the most). Parents dont generally let their 16 year old date a 21 year old
2) A lot of couples date in YU. Most girls go to seminary and many even stay shana bet. Same with the boys. When they get back, they socialize with each other and are generally within 2 years.
Are there exceptions? Sure. Both directions.
I would hazard a guess that you don’t really have any sort of proof that MO people have a larger age gap. As a 27 year old, I know in both directions MOST of the people I come in contact with are within 2 years of their spouses.