An ex-friend once did that to me with her boyfriend in the same bed thinking I was asleep and getting a kick out of it. I was absolutely disgusted and it should definitly count as harrasment. I was pretty much the involuntary third party in their game, even If I was 'asleep' and not participating. If they had asked me for consent I would have said no. And they knew that and still did it. 
So yeah every time I read that trope I'm reminded of that memory and feel extreme disgust.                                            
                                                It wasn't even the reason why the friendship broke, but it really should have been. 
I can make exceptions in fiction, but glossing over something as if there is nothing problematic about it really irks me. Especially with this trope and since some might get the idea it's an acceptable thing to do. And it really is not.                                            

		
I love smut but I don’t think I love it enough to understand the whole “let’s fuck while everyone’s asleep two inches away from us”… it’s lowkey disrespectful and I would personally consider that harassment to the people around you who didn’t ask to be put in that situation.