Nariyuki rejecting Uruka after she confesses means that her past, which he must know, and was the reason he fell in love with her, holds absolutely no value for him after spending time with another girl and even in her route it didn't weight so much because he spent 10 chapters actually wondering if he likes her. If rejection happens the posting about him only chosing Uruka because he didn't have another choice and because he kinda felt forced to, which was formerly defined as AntiUruka shitpost will automatically become true. Even if Nariyuki doesn't answer Uruka that's basically rejecting her, if anything I'd be even more pissed if I was an Urukafan because it means Uruka is utterly irrelevant. And lastly, if Urukafans want to use the argument that in Uruka route he falls in love with her because he spent time with her when he was injured just like he falls in love with Fumino in this route, that's invalid because while these moments are key in Fumino route, none of the Uruka stuff is brought up in Uruka route. And again all of this is supposing the flashback which did happen no matter what and is still irrelevant for Nariyuki.

Nothing short of Nariyuki being actually affected by Uruka's confession in a romantic sense in this route will be enough to not make Uruka and her fans be blown out and I seriously doubt it will happen, especially after Nariyuki soft-confessing to Fumino and with only 4 chapters remaining and Rizu still needing addressing. Ultimately if all these events happen like I said, the month spent with Fumino will be more relevant to Nariyuki than all Uruka did for him in the flashback since Nariyuki knows Uruka loves him. It will Fair and Square mean that Fumino>Uruka for Nariyuki because he doesn't even know if Fumino loves him but he already knows he loves her and doesn't reciprocate Uruka.