We’ll never know, since their partners didn’t go that route.
We’ll also never know if their partners would have wanted an open relationship.
I’m pretty sure that the man who cheated on me for over a decade didn’t want a poly relationship with me — I think he got off on the transgressive thrill of betraying me.
If he’d been able to enjoy all the sex with Mollie he wanted with my blessing? Not so sure that it would have been such a turn on.