Interesting points - They might have used two different types/thicknesses of leather on the vest - nothing says they didn't. One for the body and one for the flaps? Or the flaps may have had some filing put into them.
IMHO - vinyl would be a lot hotter than leather, which will be toasty enough. I'm not an expert by any means, but I should think the color would rub and wear off the vinyl much easier if it is "painted" on.
Looking at the standup and other pics - It looks to me like those areas are folded under, essentially making a double layer for the eyelet to hold onto, making it less likely to tear through.
Thanks for the link!