What you say is true in general but why would it all be true for a nonstandard relationship? Why would you be less committed to multiple persons (or why would you not have 1 committed out of all). If anything, a single household of multiple stable personalities creates more involving and colorful context, more possibility of hierarchy, and more reasons to not abandon it (as a bigger community relies on you).

I had much less direct and indirect experience, but I know what you talk about. Even more, it is also my experience that these constellations are unstable. But I see this as them existing in a sea of monogamist society, surrounded by prejudice and contempt. Try to introduce this to friends and family. It's similar of how gay relationships are much more often open, due to (guess:) societal context like a patriarchal society.

Historically disconnected societies were used to be more creative. I hope they would also be in the future.