This is something I’ve been noticing more and more. Also notice her body type if you care to look her up. “Mains” are usually more petite and fit, I guarantee you the women he was cheating on her with were thicker than her. “Mains” are the girl they like to show off for status, a trophy wife type, the “sides” are almost always thicker, yet they wouldn’t want to be seen with them.
Maybe I’m projecting a bit, when I got cheated on the girl was stacked and I’m skinny. But most of the time when Ive seen a girl that’s been cheated on she was fit or petite, and a lot of my thick friends have got their heart broken when they learned they were just the side gf.