The original series is a different author. This author did at least one BTR doujin before being hired to do the spin-off. They're not a yuri author though even then works tend to focus on pairings (not necessarily romantic). I'm simply drawing a line between Eliza's faves and their mild resemblance to a certain destitute bassist and media-addict vocalist.
Some authors do use the word "ship" flexibly for their own creative process, whether they're somehow semantically doing wrong or not, but it's not an issue here given Kesakuband are minor characters in this series.
I know, the practice of hiring doujinshi authors to write spinoffs is nothing new or unusual, especially when it comes to CGDCT or all-female titles. The point was that author still has a certain amount of freedom in the story's construction, although I don't know how wide. I think the chapter with the PreCure parody was more of an extra fanservice for those who ship Shima with Kikkuri. But of course, you can read things however you want, why not.
I still remember jokes about how one of Watamote's older volumes practically predicted the title's current development into the all-female "post-CGDCT" series, when Tomoko mocked the pandering to shipping by introducing close friends for the characters. Japanese authors are obviously aware of shipping, and I remember one mangaka using the existence of "different ships" to explain why one of her manga's pairings ended up as a doujinshi rather than a canonical development.