Poor Adachi is simultaneously stuck between "Hahaha we're just friends because it's not like I'm gay!! Romantic friendships are still no homo!" and "Fuuuuck meeee, I have a crush on my straight best friend, I'm such an idiot."
I've said this before, but I really like how the novel takes the like normally super-fluffy, yuri standard girl meets girl friendship/romance, but then makes it feel more realistic and modern by never really pretending that these girls aren't super gay for each other. Like if you just went off the plot summary it would feel pretty standard, but half of these chapters are just the girls' internal monologues working through figuring out they're gay and how they feel about that and each other.
The way I read this chapter, to me it seems Adachi knows she has a crush on Shima. What she had issues with this time is that sometimes she loses sight of the fact that to her knowledge she's just a friend to Shima at this point. Or maybe I read it wrong, I'm not sure. This isn't to say she isn't confused about the whole thing, but I don't think she's in denial about the existence of the crush, at least?
I also find the characters mostly authentic in the way you said, but so far I'm not convinced that there's an intentional theme of queer identity. So far, hasn't the explicit question of queer identity been mostly avoided (as it is pretty standard for yuri)? Though I can recall moments that imply that this is at the back of her mind, such as the repeated "I'm not like that" disclaimers in previous chapters, and wondering why she doesn't feel the same way about her other two friends who are also girls as she does about Shima.
It might come to the forefront later, but it's not like it would stop being "good yuri" even if it never did. There's a lot of yuri that can feel relatable without explicitly dealing with queer identity. (I suspect if this weren't true, there wouldn't be such a huge LGBTQ+ contingent in the readership here.)
I mean Adachi is definitely mostly just focusing on her feelings for Shimamura, but there's also been a few times when she thinks of the implications beyond that too. I'm too lazy to go find the chapter right now, but there's that one scene where she's thinking about how her being Like That would be tough on her parents or whatever, that very Japanese sort of homophobia. There's been a few other lines like that too. And then there was Shimamura's story about what is clearly her first little girl crush back in the day.
It never really dwells on it, but I feel like there's enough there to at least reassure me that the author thinks of them as definitely gay, and not just like, a cute phase or only attracted just to this one special person. Which is enough for me, especially since right now the two of them are still trying to be honest about their feelings for each other, so it's a bit much to expect them to already be looking at like, the bigger picture of what that crush means to their identities.