Maybe its just because I'm a dumb cishet, but I didn't read Spinel's relationship towards Pink as romantic in any way. Spinel isn't Pearl. The show already did a story about romantic abandonment with the same damn character (Rose), so not only would it be redundant to do again, but we already know what it looks like and the Steven Universe movie wasn't it. Pre-abandonment Spinel is also, as the tumblrites would say, "child-coded."
And I haven't seen a single person of any orientation question the plot point the post is referring to. So they're at most arguing with one actual person who hold this dumb view. Somehow that constitutes the "The Straights".