men should be allowed to chose underwear to make them feel pretty
They are not being marketed at men who want to feel (or look) pretty. Not to effeminate gay men, or effeminate straight men for that matter. Fashion being fashion, some of my (neither effeminate nor gay) ex-DPs wore pants like those back in the 1970s/80s (but less saggy fitting) So it's marketing them as "trans" that's weird. Or sad - that just wanting to wear men's pants in nice colours makes you "trans". Those pants don't look like fetish wear to me, unless the world has become a lot more restrictive while I wasn't looking.
But what really gets up my nose is that it's so fucking coy. They could sell pretty clothes to men, or plain clothes to women. They could openly market to feminine men or feminized men, or to masculine or masculinized women, to people who want to look pretty or sexy or outre in their undies, or to people who don't give a flying fuck as long as their undies fit and are comfy. If they are really aiming at "trans" people they could make it very clear if they're selling frilly knickers with extra space for your schlong, or boxer-style shorts for women with or without codpiece padding.
Instead their "trans" label hides it all under a layer of po-faced dishonesty. Like sticking frills on piano legs.