I was one dating a girl on the side of my primary relationship, and we never got to the place of having sex. It never got past my "feeling her out" phase. She talked all big and great about poly this and poly that. She had all the theory and concept down.
But, when it came down to it, she couldn't do the work. She couldn't actually tell her primary partner the reality of her feelings. She couldn't be honest with herself. She couldn't walk the talk, essentially.
Perhaps i could say that she was in a phase or layer of her poly process unfolding in her life. I think I was there once too, that's why I say it. Once when I was new to all these ideas, I espoused them vocally, but the reality of living the integrity and open heart raw and maybe dangerous communication required was still beyond my abilities at that point.
Is it so with this man in your life? Is he new to poly?