It’s called “Man-splaying”, not “Man-spreading”, not to be confused with “Man-splaining”. Yes, it’s an actual thing.
I noticed it within a few months of moving here. I asked my husband about it. He said it’s usually due to men’s big stomachs and being overweight. Their thighs are taking up all the space needed for his junk….so, the junk needs some space. Thus the need to splay themselves.
Hope that helps….