Free Eternal Abs reminds me that these shows serve as idealized entries into homosocial circles more than anything else. In the same way that shoujo reverse harems allow me as a male viewer to understand the mechanics of gaze is a relatively guilt free way, Free really does let me look at the four/five girl shows in a way that allows me to be completely distant from any emotional (or admittedly hormonal) response.
Since this isn't sports porn like that Yowapedal or Haikyuu, you can't really say that Free is about the art of swimming. Even something much "baitier" like OoFuri had baseball porn to have it be more than just a brood of boys hanging around with each other.
But Free doesn't really have that problem. It really is focused on an idealized representation of homosocial bonds that is literally about cute boys doing cute things. Even Kimi to Boku had romantic entanglements and love triangles to at least create some sense of conflict and narrative drive for a show about five guys hanging out with each other, but here the show is absent any female figures that can threaten the safe idealized male friendships that are presented here.
People talk about guys ruining Love Lab, but I think that speaks to the fact that the protective homosocial bubble is burst by the intrusion of sexuality that threatens the active and engaged observer. If Free is very much about a window into how boys might live their lives, then a presumably female viewer doesn't want to see them talk about the girls they want to have sex with or the sexual desires that they might have. That's not to say that the female viewer necessarily thinks that these characters are their "husbandos", but that they can just see these characters as idealized men absent of any of the negative connotations that can come with being attracted to a real live human being.
And yes, we have Gou and the teacher that serve has female figures in the show. But Gou very much serves as the audience surrogate, much like the various all-girl shows that happen to have one male lead in them like GJ-bu. They exist to reflect the viewer back at herself, and allow her to feel like an engaged observer, but again without any of the icky entanglements that plague real life. If one wants to be reductive, it is very similar to the socalled "hag" who loves have gay male friends, because she is able to penetrate a usually homosocial space without any of the threatening sexuality that can plague typical relationships. There is no expectation that Gou will hook up with or sleep with any of the guys in Free, or the guys being attracted to her in any way. She's just there to admire them and their bodies... to the point where her admiration itself is more aesthetic than sexual.
This is all very different than the harem/reverse-harem ideal where there IS sexual desire and the idea is that the text serves as emotional porn for the viewer. These shows exist to allow the viewer a glimpse into a life that they do not necessarily have access to, but in such an idealized manner that nothing is allowed to threaten that space.
The Love Live girls have sleepovers and pillow fights, but never play truth or dare about the men that they might want to make out with. They just exist as signifiers of idealized feminine behaviour, much like the men of Free are idealizations of masculine behaviour.
It's all just very interesting to think about and in part crystallizes why the all-girl versions of the show works for a lot of people (and admittedly, for myself included).