It sounds like you expected a V, and he expected something more like a triad where everyone sleeps with everyone? If that is the case, then what is there to apologies for, really?
"I'm sorry that I have boundaries and enforce them." isn't really...I'm not sure that I could say that in a way that could be taken as an apology, myself. I suspect that I would be angry at him too.
I'm dating two guys. One is single, but poly and looking, and the other is married. His wife and I are friends and nothing more. She is poly, but, her boyfriends are out of town. I'm not sure what typical poly looks like, but, that's ours. I happen to find it easier and less stressful to live on my own. A situation where I was living with others would have to include a large enough space, and very firm boundaries or I would not be happy.
Mostly I am including the personal stuff because I think that lots of people move in together right away, and that does not always work. Sometimes it helps to take it slow and figure out what your needs are and how to ask for them before you are actually sharing living space and figuring out whether the toilet seats belong up or down, and who left the laundry on the floor, and who does the dishes tonight? I know I need my alone time and I can ask for it....now. Six months ago? I might not have been able to ask for it or felt able to, and the lack of alone time would have been a problem for me.