The Diaper Fold term never made sense to me. I think using a diaper to illustrate the fold isn't a good example. A diaper is flat.
Here's what I see happening. Take a piece of clay and roll it out in a short coil.
Pick the 2 ends up and press them together so you now have a doughnut shaped piece of clay.
If the "glob" is in it's tire/doughnut/cheerio form before it hits the rollers.
It'll look like it only has one seam. If the the "glob" is still in the rolled out coiled form
when it hits the rollers(like Scott Meyer's) you're going to end up with a single stream Swirl that only shows one shear mark. Both ends of that "stream/drip" glob
never have a chance to meet.
FWIW