@SuperOniichan as a wlw I can confidently say that if the genders were all flipped (i.e. a father thinks his daughter is gay) with the exact same personalities/plot... I'd still enjoy this manga, 100%. I don't think it's fetishizing gayness at all. It's made abundantly clear by the mangaka that MC is, in fact, gay. From my perspective, mother isn't projecting her fantasies onto him at all. She's simply a kind, loving mother who wants the best for her child, and doesn't want him to feel as if he's "freakish" or "unnatural" for liking a boy. Isn't that something to be celebrated, especially when compared to actual fetishizations of gayness that call it "forbidden love" or "sinful?"
If it WAS fetishization, the mother would have ACTUAL fantasies, such as imagining her son kissing a boy, then blushing and thinking to herself "oh my, forbidden love!" or "I'm going to the sinbin, teehee!" But she doesn't do that. Instead, she treats it as any other crush that her child might have, and simply tries to support him in any way that she can without making it clear that she knows he's gay. She treats the situation very delicately and tries to not out him before he's ready to tell his family himself, understanding that doing so would be intrusive, and might make him uncomfortable. She understands that growing up gay in an environment that is sometimes hostile towards homosexuality (e.g. the childhood crush flashback) can be hard, so she does her best to be a constant in his life-- someone he knows he can always trust to love and care for him.
I was rejected by my family for my sexuality, so I find stories like this very cathartic. I'd relate even more to the story if it was "My Daughter is Probably Gay," because it'd parrot my struggles with my sexuality and my family (albeit in a more gentle environment with a loving parent instead), and it wouldn't be creepy at all. If what
@Sem mentioned was true (that Okura is a gay man) then this story might be a way for him to recount or rewrite his own experiences growing up gay in a society that views it as odd or weird.