I'm not aro but if I can offer a perspective on specifically the Epilogues (because I think a lot of the stuff mentioned about HS's perspective on this is true) - I actually think the lack of clarification on Callie and Roxy's relationship serves an important purpose to some extent. IMO it's reasonably safe to say they have some sort of queerplatonic relationship that feels very secure to them, but since our POV characters are outside of it they mostly express befuddlement. Like, it should maybe be stressed that the sentence in question as being alienating is from the perspective of John, as written by Ult!Dirk. A hugely recurring theme in the Epilogues is the almost complete lack of ability for most characters to envision anything outside heteronormative relationships. The anxiety over not knowing drives a lot of John's actions and his conversations with Terezi, when really if he just sat down and had a conversation about multi-partner or platonic relationships, it all probably would have worked out (think of his flirtation with Kismesitude at the end of Act 6 Homestuck). But, John "I am not a homosexual" Egbert refuses to have these kinds of deep introspective conversations about romanticism and sexuality and gender, and would prefer to pine over women from afar. I'm sure she has completely normal reasons for this.

The fumble I think is due to the Epilogues deliberately not offering any closure on this front...all over the place it wants to use polyamorous or other nonstandard relationships as fuel for drama without really examining them because it's intentionally from that limited perspective. Or when it does, it's toxic (Jane taking Gamzee as a kismesis, thereby neglecting Jake). Jake's already been mentioned but I think Karkat may apply as well, he's clearly fascinated by romance despite an aversion to it, and it's pretty consistently framed as a hurtle for him to overcome rather than being somewhere on the aro or ace spectrum.

My hope for the future is that Beyond Canon eventually circles back around to offer other perspectives to serve as a counterpoint to what the Epilogues are doing...it's something Homestuck as a whole could improve on for sure