Ah, I had seen it as part of a list of "myths" about poly people. I guess the myth was that all polys do it? Or maybe that it's the only type of sex when you're poly?
I can definitely see how there is more possibility for it in a poly relationship than a mono one, for obvious reasons...
I don't think I would want to have only sex with the three of us at once, or even mostly, or even half and half. I think it would probably be relatively rare but that it could bring us all closer, so I'm looking forward to it despite some apprehensions (as always when something is completely new and non-traditional).
I'm glad to see other people here have experienced it and enjoyed it