I did feel like he was being evasive. Thank you for the advice to ask him what the other women's expectations are, I like that way of approaching it.
Do most folks do full disclosure with FWBs? I have a couple FWB, they know my situation and I fully expect that they are seeing other people, but we don't discuss our other endeavors. I thought that such a relationship comes with the expectation that it is not exclusive (necessarily). That being said, I am concerned about whether he would disclose the true nature of the relationships. Thank you for confirming that the status of the relationship is not the important part, I obviously do not meet married men unless the wife knows about me, and I was feeling uncomfortable if it was a girlfriend, but was questioning myself about whether that was extreme.