With Sage I guess the expectation were just different, and as always the long wait didn't help. Throughout season 2 she was progressing to be more romantic and sweeter. If you pick her in ep8 she talks about going on dates, cuddles, stuff like that. Then in ep9 we get the Sage who wants to be called a slut and getting fucked in the ass. While it's still in character, it's quite the whiplash from the last time MC had a 1 on 1 scene with her.
Both sides have merit. Ep9 was a halloween party, so it makes sense she was horny/slutty. But I also can't fault people who wanted sweet Sage after how things ended in ep8.
In honesty, She never wanted that. She knows MC wanted that from her so she tries to give that to him. Reason why, at the end of EP.8 She is kind of feeling awkward to tell him that she wanna fuck. The reason why she feels embarrassed to tell him that is because she thinks if she does tell him that, it is not gonna be what he wants from her.
I suggest the player to stop looking at a character with his expectations in mind and start seeing what the characters really are. It happens in a lot of RL relationship as well. People never try to understand or accept the other the way they are. They want them to become what they want, as if they own the person.
If you have a gf who is popular, who talks to a lot of guys and girls. You can not expect this girl to stop talking to guys only because she is in a relationship with you. You can expect from her to respect your relationship, by not cheating on you, kissing or having any sexual interaction with someone else, unless you both agreed on that. But you can't expect the person to change who they are because of you.
With that in mind, the same goes for Sage. Since ep1, all she wanted was someone to fuck her. Chad never gave what she wanted, she offered that to MC. MC then wants something else from her other than sex. That is not what she wanted. But she said she'd try. Then a frat halloween party happens, where all you do on these parties is get drunk and try to find someone to fuck, you are judging her because she wants to fuck and have anal sex with her boyfriend.
Some people are upset that she was trying some fetishes with MC. But didn't she and MC had talks about their fetishes before? Didn't MC tried to fuck her ass before? So why this bothers everyone that she wants to give him her tight virgin asshole in the end of the night of a frat party? Shouldn't he feel special for being the first?
She cannot changed who she is because of you. Both have to make efforts. She is trying on her side, you should be patience and try on your side aswell. People aren't there to serve us and only the things we like. That is not how the world works.