The variance in label sizes is definitely more extreme in women's sizes, but I'm particularly struck by how it happens with supposedly-objective men's clothing. As men's pants get larger, the waistband size becomes increasingly dishonest - despite supposedly being measured in "inches". I'll look for the study, but it can get up to an impressive 10%+ discrepancy.

Not to mention variance within a given labeled size itself. Last time I went shopping for jeans, I tried on two pairs from Levi's with the same cut and labeled size. One was too tight and the other was too loose.