Like you, I don't have a pair of MIJ raws for reference, as I only own a pair of Silver Selvedges. However, I can say that the denim on them is super thin & soft when compared to the MIJ raws I've seen in stores, and especially so when compared to my APC hipsters. The crotch blew out after about 15+ months of steady wear, and I also developed rips along the creases on the back of my thighs. By comparison, the crotch on my APCs also blew out (around 18+ months or so), but the denim on the thighs and everywhere else is nowhere near the level of thinness on my Diors.
To be clear, I like the Diors a lot - they're super comfortable, and I dig the fit, and they've faded nicely. I don't think the denim is necessarily poor quality, but it is quite thin, and not nearly as hardy as other jeans I've worn.