>I also really think that observing that websites often act differently when you’re not focused on them is a pretty standard-level observation
Agreed, and I would guess that is the extent of what people do with that observation. They see it, and have no clue why or how or what that means. Is it only certain browsers that do it, or does it depend on if it's a phone or laptop? Maybe it's a AT&T service feature on phones now? Or maybe just iPhones do it. Maybe it's only on previously visited sites? Or maybe it's a virus or a scam of some sort.
People with no frame of reference see things very differently. It's a magic box.