May be blanf but

It did though. In the first chapter. He wasn’t really consenting with enthusiasm now was he.

You got my point wrong.
In any other omegaverse bL it more extreme than what happened in the first chapter.
The seme literally blames the omega after what they did plus- This alpha right here, in the first chapter itself, his behaviour showed us that. He is atleast not one of those trash Alpha who thinks only on their instinct and go all the way to putting it in on the first encounter.
The alpha in this chapter knows that he shouldn't atleast put it in* and he didn't. He didn't let his instinct take him over to just because of a mere "his an omega I want to do it with him".
We all know, alpha's and Omega's are unconsciously drawn to each other and more drawn to each other if they are a fated mate which confuses their action and outcome because of their pheromones.
And if you found the first chapter's action as an extreme form of SA assault, then you haven't yet actually read the REAL SA of there omegaverse bL.

SA means in the form where the other party assaults somone and refuses to take responsibility of it and chose to ignore what he has done and blame it on their instinct.

I mean.... in your comment you said that at least this didnt have any SA or grape and I'm just replying that yes it did. Regardless if other omegaverse stories have it worse.

But think of it deeply.
We're talking about SA in an omegaverse comic.
If it was any other genre, then yes I'll support it fully of being SA.
But as you can see, the uke here is an Omega and we know Omega's are automatically attracted to alpha.
We could clearly see that the uke was attracted to the alpha from the beginning but he was denying it.
SA is considered a touch that makes you extremely uncomfortable to the point that after the touch, you feel like you've being stained.
But the reasons why I didn't considered this too much is because it can clearly be seen that the omega was interested in the alpha but he denied it because he wants the alpha to meet somone more cute. The uke was also sexually attracted to the alpha but he kept on denying it and making it seems like he wasn't worth the alpha's time and care.
And yes if the alpha wanted to forced upon himself, it wouldn't have been just jerking him off, he wuld also have fingered him trying to force f him too witout even caring about the uke's feeling.
Alpha's shows their attraction and love to their omegas in this way. (Not all Alphas but certain some because omegaverse is clearly a genre related to animals)

I hear your reasoning but I still disagree. I would still consider this as SA. I've read omegaverse stories where there's literally none. I'm not blind to the fact that yaoi in general tends to be grapey and the story logic doesnt change that. It's still SA. I usually roll my eyes and skim the rest or stop reading.