lots of great responses here. i want to circle back around to the OP's point about circumstantial simultaneity. maybe this is my own bias but i've always understood that term to be a broad narratological concept for helping the audience to understand that events displaced from each other in linear time are still meaningfully connected to one another. it is, essentially, a technical term for what's occurring in-fiction when an author parallels seemingly unrelated events for the sake of the audience.

like in a movie with multiple timelines, you might have a ticking clock scenario happening on one layer while a big fight is happening on the next, and the film is rapidly cutting between them for maximum dramatic effect even though in-fiction they might have occurred many years apart. "circumstantial simultaneity" quantifies that symbolic relationship as something that carries material weight within the text itself, to the point of being something characters in the story can take advantage of to their own benefit. but that doesn't mean that all the circumstantially simultaneous events in homestuck are equally meaningful. in any text, there is always a point at which symbolic analysis starts to break down.

calliope is an echo of the ideal "good" reader, one who yes-and's the text, and i think her trying to read into the penis ouija is important to establishing that even a good reader can miss the mark when they lack cultural/historical context or are too enthusiastic in trying to suss out every possible way in which it's brilliant. i don't think homestuck hates us for reading it, but rather that it has an opinion on how seriously we should take it: at times, very; at other times, not so much. everyone pushes too far in one or the other direction eventually, like a bathysphere sinking too deep for the pressure rating of its hull. the adversarial nature of homestuck is just the text's way of reminding us that no framework of meaning can be applied universally to every single situation, and sometimes you just have to be willing to shrug and say "yeah that's just there because they thought it was funny"