The thing about Futaribeya is, while the author always visions the mains as being in a relationship, Editor-san comes in and said "Nope, please turn down the yuri."
I don't know if you have a source for that or it's just speculation. If you do read it somewhere, you probably misunderstood it, since it would be pretty unprofessional for Yukiko to say her editor asked her to make it not-yuri, since probably a big part of her fanbase are yuri fans. The editor might have asked her to tone down the yuri, but that would just mean that both recognize the work as yuri, but it's not a romance or drama story, so she shouldn't do yuri scenes unless it's relevant to the 4koma format. In the end, that's how it is. It's a slice of life manga, and the media isn't known for genre shift. In fact, a lot of japanese fans hate having their expectations betrayed.
Also, about yuri mangas not being able to full their potential in not yuri magazines, it's not true at all. Let's not forget that things like Bloom into You and AnoKiss are works in not yuri magazines, and they're more successful than most Yuri Hime series. It's a shame for Morinaga, but she was never popular in Japan. And as much as I love her stories, they're all too similar. Yuri Hime cancels a lot of series, too, so it's not like it would be different in a yuri magazine.