The scrotum is amazingly variable so it can stretch out thin and loose and kind of shiny with no wrinkles but then crinkle up and even double crinkle to minimize surface area. From a limp balloon to a thick dried apricot typically. Unless you have someone down there taking photos, you really don't notice the changes. So there's nothing involved in this area with a circ. Different skin. And it's not the sack that pops em inside.

Separately, tendons run the balls up and down like an elevator, like when you tighten your lower abs. Sure, when the sack is tight, they are up, but they can zoom up and hide even with a warm, relaxed sack. Doesn't the government give giant grants to study this stuff so we don't have to spend time with our webcams when in the middle of the pleasure zone?