It's worse when you realise that one manufacturers XL is different from another, and even worse when you realise that it even differs within a brand.
It's gotten to the point that you should only ever buy fashion online if you can return it and even that is fraught, since plenty of customers wear an item for an occasion and then return it.
If you do buy something, make sure that you wash it before you wear it.
It makes me wish that brands weren't so separated from manufacturing. I hate finally finding something that works for me, ordering what should be the same thing only for something obviously from a different factory with major differences to arrive. It feels like just about everything is white-label these days. White-labeling undermines consumers' ability to make informed purchases.
Pretty bad when its L/XL/XXL or 4/5/6, but 48/50/52 etc. should be standardized inches (with a little wiggle room for discrepancy, because fabric ain't concrete) which can be converted to centimeters. Still, it'll only give you the measurement of the waistband, not anything below it, nor if it will stretch.