That seems way too simple for me. There's often more than two people and more than a single event.
For example, if my partner is with someone else, I'm taking 1) the time she's not with me, 2) the joy she's experiencing, 3) worry about her liking them better, 4) experiences I'm having while she's gone, 5) worry about them coming home safe, 6) joy/pain/indifference for the (in T's case, I'm happy for her primary, happy for J, varies with G, unhappy with R (he's a liar))
And that's just off the top of my head.
Sure if you could distill it down, maybe you're right, but these aren't simple interactions.
Me: 39 straight male in a V with
Wife: Kay - mono female - married 17 years
LDR girlfriend: Susan - poly female - 3 year relationship
Stakes - very intimate friend