I like that this is a male posting, and I like that the subject of advertising related body dysmorphia (in its wider sense, not objectifying the OP) can be discussed as a gender neutral topic.

Companies which use ordinary people in ordinary size ranges are much easier to trust and buy from. Companies who set up unrealistic body proportion goals make it hard to know what "fit" is available.

A niche class I've found which seems to be appropriately dimensionally accurate is mail order leather jackets. They give you as much help as possible to understand fit across the body not just S/M/L. Maybe it's motorbikes or maybe it's the return business from happy shoppers, or maybe it's the high unit cost.

A now dead regional Australian clothes and footwear company (rivers) used to use staff as models. All shapes and sizes, all ages. I felt I could relate to the fat guy from marketing in that shirt, the same with an outfitter called Lowes who used ageing rugby league stars, who generally grow a beer gut and carry a lot of ex-muscle. I knew a shirt from there was going to go with my bald spot just fine because Wally Lewis modelled it and he had the bald spot from hell. I didn't have the muscle mind you but that's on me, not them.

sigh American car culture.

I have the same problem and I'm only 5'11" (177 cm). Size "Small" might fit at the neck/shoulders but with lots of extra fabric around my midsection, but most retailers don't carry much inventory for Small, and almost never have Extra Small. In the SF Bay Area, the small items are always out of stock.

At one point I found that clothing boutiques in the Castro tended to stock clothes for skinny guys, but those stores disappeared during the pandemic.

Now I have to go shopping in Seoul or Tokyo or NYC, but if the pants fit in the waist, they're usually too short.

Is it common to say how tall models are? I just checked a few sites, but not seeing it.