Except twitch's guidelines specifically state
LinkInappropriate Broadcaster Behavior and Attire
Nudity and conduct involving overtly sexual behavior and/or attire are prohibited.
And that's been around since before Twitch had an IRL section after they had to crackdown on both male streamers (not wearing a shirt whilst streaming) and female streamers (visibly undressing to their skivvies because they needed to "change" and "forgot" they were streaming or wearing extremely revealing clothing) a couple of years ago. The thing is Twitch has gotten lax on policing it's own policy and has been in some cases extremely lenient in their punishments causing some to question why.