The point of evolutionary framing is not that we have evolved to think about these things, but that they are biologically ingrained such that they incline our entire experience of living without conscious thought.
> Geography plays a role
I believe the article states the opposite is true: more children live closer to their paternal grandparents. I was surprised.
Where do you live that all the married guys live so close to their wives' families?
In terms of physical distance, our order is: (1) my father, (2) her mother, (3) her father, (4) my mother. None of them are that close – my father is about an hour away; for her mother, add about 10 minutes; for her father, add 20; my mother lives 3–4 hours away. At least they are all in the same general direction.
In terms of how much we see them, the order is: (1) my father, (2) her mother (although only a little bit less than my father), (3) my mother (a lot less than either), (4) her father (we haven't seen him in > 18 months)
Seeing her mother more than her father, and seeing my father more than my mother, is mainly due to the quality of relationship each of us has with the respective parent.
"Maternal grandmothers were significantly more inclined than paternal grandfathers and grandmothers to maintain frequent face-to-face contact, as distance between grandparent and grandchild increased. " [1]
[1] https://journals.sagepub.com/doi/full/10.1177/14747049070050...
It's 'Mother Tongue' nor 'Father Tongue'. Women raise the children, they're more likely to raise them with their family members as well.
Geography plays a role: every married guy I know lives 3 streets over from his mother in law, I think actually it's more common for couples to be near the woman's family.
I suggest this is one of those kinds of things, if you were around 100 years ago, would be kind of dead obvious to most people.