It's intentional, to force you to engage a salesperson, and that salesperson knows all the jargon and unnecessary variations and how to size clothing that fits you. Once you have a positive transaction like that, it gives the company the opportunity to get a very loyal customer out of you, and it's the more pricey and "exclusive" brands. 100% emotional manipulation - they piss you off on purpose so they can seem like a hero and set you up with clothing that feels and looks good, but the specific fit will only match their numbers, and maybe even only their numbers for that season. How about ensuring that you can match someone who wears XL with an L right after holiday season, or hit them with an XL in the fall to set them up for a change during the holidays, etc.

The schemes are ruthless and never end, and it's all arbitrary fashion. In some ways, it's a lot easier being a guy.