Two of the four OF accounts seem to just be the athlete sharing behind the scene details about their Olympic journey and chatting with people. Not so clear for the other two.
Other than one of them having "artistic portrayals of nudity", but saying that "Explicit sex acts will not be part of [his] content", all of them seem SFW
So I've never logged into OF, but I would imagine there are quite a few pages where you get something similar experience wise. Attractive person fully clothed says sign up for my of to see more. Sign up and it's pics of them in their underwear
I remember OF saying they were banning NSFW stuff (or something to that effect). It's possible they market themselves as something like Patreon while being one of the only platforms that actually allows NSFW content.