I mean, I have drank pretty heavily over the course of my life, and I never understood blackout drunk until it happened one time. At Blizzcon like 5 years ago I was drinking literally all day at a guild's house they rented, I remember that, then the next morning I woke up in another friend's hotel room on the floor. It was over a mile away. I walked (with help) that mile, made it to the 10th floor of the hilton, partied more in that room (fell in the tub and yelled to be helped out apparently), and then passed out in the kitchen with pizza and beer on my face and lots of pictures of it all.
It absolutely happens. Hasn't happened before or since, but now I know.
I think a lot of people probably think of blackout drunk as 'oh I'm a little fuzzy and my memory is harder to pull up', but "Hey, I just lost 5-6 hours of my life into the void" absolutely happens.
There are different levels of drunk, and different people will reach those points at different times. I can be drunk and know what I'm doing, but "Hey they look passed out, or completely incoherent" is long past that point. The fact that he's still physically able to act on what is going on and she seemingly wasnt, is a clear signal that she's no longer consenting. Period. Like, you can't even say 'he can't consent either' - he's the one fucking doing it if she's literally unable to do anything.