You are right in that this is pretty far-fetched. Rin keeping to herself doesn't mean the rest of Idol does. EN Gen 1 is overall more distant but the Idol girls will frequently collab, planned or unplanned. Riro, Yuko, Fuyo and all of Gen 2 are especially close. Pochi is more on the anti-social side and Rin is Rin so they keep to themselves. I'm honestly not too sure about Juna but she'll show up for collabs every so often. Even the HE girls will collab occasionally whenever Katta isn't busy searching for Seth #09516. I'm fairly confidant in saying that Rin is an outlier but if someone oshis one Idol girl, they'll watch another one or two at the least.
This is obviously a Phase-oriented place with actual Idol viewers being a much smaller percentage. Because of that, the main impression we get of Idol is either from numberfagging, Yuko being a degenerate or Aviel flexing his shekels on Twitter. Ultimately, these Phase vs Idol comparisons never mean anything and will always reach the same conclusion of "Rin has more subs but Phase is doing everything better" so it's funny to see how many times it's been a topic of discussion.