I don't have the heart to go Singleship with my OCs hahaha. It's interesting to see the different interactions, reactions and how the story would or not would be changed depending on the other chara.
However, the Rule for multiship is keeping everything in its own universe, after all. Cheating? Jealousy? Involving someone else's chara? Not really happening.
Whether you want to call it "canon" or not it's really up to how one interprets it, I believe. But I also think that it's kinda part of the responsibility and respect each writer/creator has with their partners and vice-versa. If the other part is ok with me having 10 different canon ships, I will also be okay with them doing the same.