Yuka and Eri also appear in that flash forward. Cutting back on characters to focus on another person's story isn't making that person a main character, or the others side characters. It just means that you're giving a certain character depth.
For example, if KS suddenly said "I'm cutting back on a lot of the girl's stories to focus on another character" and the next update, Harry had like 75% of the screentime, that doesn't make him a main love interest. Or hell, female interests, if he had mc hang out with that one girl that you helped in the beginning.
Edit: I do kinda understand why that would make people think of her as more a main girl, plus she does appear in plenty of image spreads on the patreon so perhaps she really is a main girl. Idk.