Hmm, I think I see what you're saying. But, I mean, as long as they're each involved with you they *will* share that bond of being metamours, whether they choose to acknowledge it or have a friendship or not. They can end the connection between each other by breaking up with you but they can't stop being metamours otherwise... that's what makes it feel similar to me, is that the bond is through another person and they can make of it what they will from there, good or bad (hopefully very good!).
"I am afraid to find it to be true in later times because they just don't like this or that about the other but don't see another way of handling things and therefore put up with it." <-- There are things I don't like about my roommates, my friends, my metamour, even my lovers. If it's something that's possible to talk about and work on, and it's important enough to try, I may do that. Or I may just accept it/put up with it. Isn't that normal? What other option do I have aside from walking away? No one is perfect.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.