Hell, even this chapter has Adachi going on about doing the cavalry battle with mixed gender teams in swimsuits and the capture target being a girl's bikini. Don't even need to look back 3 chapters ago for his sexist BS. He's literally just objectifying women moments before this challenge, regardless of whether he's with just Ichikawa or the other boys or whatever, and ironically trying to qualify it by claiming 'progressive era'.
Yeah, he seems to be realizing how dead-end his shitty perspective has left him, I suppose. This is definitely important for his character, and clears the air even more, so to speak.
The anime manages to do this chapter's contents pretty decently, albeit shuffling things around so the flashbacks happen near the end when Adachi brings it up and Anna checks on Kyo's scar on his arm from the injury. It flows very well narratively. I even like how they added interactions between Kanzaki and Oota in this moment to help spell out Adachi piecing things together, starting to realize he never stood a chance at getting Anna's attention, because Kyo was already there.
This challenge isn't really a contest for Anna's heart, as Adachi seems to already be starting to come to grips with the fact that was a lost cause from the start. It really is just closure for him. Not that boys fighting over a girl would be any valid contest for love, anyway- the girl chooses who the girl chooses, and Anna had long since chosen Kyo by this point, regardless of when she realized those feelings.
The flashback itself is a great piece of evidence on the road to our current state of affairs. At the very least, that's potentially the start of her appreciating Kyo as a good person, in addition to acknowledging his existence beyond just 'random classmate', and it was months before I think their fateful meeting in the library, I believe, at the very start of this story.
Seeing Adachi realize he also needed to apologize for at least one of his shitty takes with respect to Kyo is refreshing, as well.