I think a lot of them were folded, ends in as intended but over time, when handled, formed small little wrinkles at the mid-point. It just makes sense that if a T202 is bent at all, with ends folded in, it will give in the middle (forming a wrinkle) since that's the weakest point. I've got a lot of 2s-4s that look like 6s, but only have that tiny/minuscule wrinkle down the middle.
Also have the ones with a fat crease down the middle, so agree with others that some people just folded them down the middle.
Regardless, I love me some T202!! (and think they deserve more attention as little works or art/action shots, and great bios) This one just arrived in the mail, the last Matty I needed.
T202 Mathewson Fletcher PSA-5.jpg