Hell....
....We don't even have universal sizing in this country.
We used to. A 32" X 34" pair of men's jeans was just that. A woman's size 10 was the same in every brand.
Not any more - we now have what is called "vanity sizing," meaning that the label is a flat-out damn lie intended to salve the feelings of those who aren't as svelte as they'd like to be. In some brands, a "medium" polo shirt is really an "X-large." A woman's size 4 is actually a size 10. A pair of pants labeled with a thirty-four-inch waistline may have one two or three inches larger.
The problem is greatest with the most expensive brands, which presumably have the customer base least equipped to deal with reality. I can remember when I could order clothing from catalog companies like Sears and Penney's, and be absolutely certain it would fit acceptably well. Now, you really have to try things on first, because you have no idea what the true size is.
Even if a brand's fit is okay this purchase, it may not be next purchase. The brand may go from true sizing to vanity sizing, or it may switch countries for production, meaning that the new nation's idea of what fits an American butt is not the same as the former nation's was.
It's all very frustrating, and I for one wish we had size standards codified into consumer law, no fudging, no fooling and no wishful thinking allowed.