That's textbook SA. Ian didn't agree to having sex while unconscious beforehand so it can't be treated as a somno kink thing. Ian doesn't even know about that. Jo didn't admit to it, just going along with 'you just fell asleep' (even though he makes the distinction between falling asleep and passing out in his internal monologue). Ian even tried to protest before passing out: saying he can't go anymore, changing the subject (it seems like he's uncomfortable with outright declining so he likes shifting focus to sth else: like TJ inviting him for dinner in chapter 21, this scene in chapter 52 when Ian asks about the camera and chapter 58's "Let's go out... We're out of coffee, too", all three times there's a change of subject), calling Jo by his full name (I believe it's the only time he does that). And once he looses consciousness he can't revoke consent (or express consent to what's happening) so... Yeah, SA.
How do people read this and root for Jo tf