In his defense, I suppose a certain amount of small material (including a few little rocks) would probably accumulate over time, hidden by the clover. So that part's kind of fair, I guess.

Just that, if you don't need to actually mow it, then what matters it? If I had to speculate, I'd guess that he was used to a lifetime of grass lawns, felt a comfort zone there, and was always a bit uneasy about the clover lawn. And yet, didn't feel up to arguing that with a certified Master Gardener while she was still alive.

That's the rock fairy bro. That or if there are already rocks they, you know, breed and stuff.

He's probably had some experience with moles. They're so small but they'll fuck up all your landscaping. And they do bring small rocks up with their mounds sometimes.

In a certain part of France, yeah, kinda. Not just rocks either. Unexploded ordinance from WWI and WWII resurfaces every spring when they plow the fields.

Of course not mowing the clover, and not plowing or cultivating the field solves both of these problems.