It could be a number of factors interacting.

For several years, I worked part-time as a flat-fixer at a dump truck company. Typically, the truck tires were run with 85-100 psi pressure. I can tell you that high pressure does not prevent flats. I've heard people argue that it helps cause them, don't know if that's the case, either. But dump trucks do have lots of flats.

I don't know how you'd go about establishing this in a proper fashion, as you're always going to be comparing apples and oranges (or more properly, apples and pumpkins). They simply don't make the same identical thickness of tire in totally different sizes.

Over the weekend, I rode 35 miles on an organized ride with my 26x2.125" tires- and no flats. But I did pass a half dozen people who were stopped fixing flats.