You think it's sexual assault if a woman is drunk and asks you to kiss/have sex? It's taking advantage of her because being drunk completely absolves you of any responsibility. Obviously if they're passed out or barely conscious, it's rape, but drinking alcohol doesn't mean you can't make any decisions and everyone else has to protect you.
To answer your question (and here are the photos again for anyone who didn’t see the original post).
If you’ve seen the movie -
1. She had repeatedly made it clear that she wanted their relationship to be business, nothing more. Sure, she can change her mind, BUT -
She WAS totally wasted. They make a point of how smashed she is when she throws himself at him
3. She WAS barely conscious at that exact moment - she passes out literally seconds later.
Recognizing this, Austin is going to wait until she’s not out of her head so he knows she really does want to have sex with him.
Another guy in comedy who knows where consent is at: Evan from Superbad. In this case, he even knows that the gal is attracted to him and that they both want sex, but at the moment she’s so smashed that her decision making is impaired so he wants to wait until she’s not out of her head, same as Austin and Vanessa.