What are you expecting? And why are you expecting it?
I'm assuming these correspondences were sent via text message, and the first thing I'd say is that text is usually a poor medium for serious communication. If I'm hearing you correctly, you asked him if your proposed plan/s conflicted with his, and he responded with a short, concise piece of information about his plans (what time he was going). His response would say to me: "No, your proposed plan does not conflict with any of mine. I'm going to arrive at approximately 8:30." I'm unsure as to why you are expecting him to bring up a potential insecurity of yours, especially in a medium of communication in which short, concise messages are the norm. If you want to negotiate something of the plan, just start negotiating. Why are you expecting him to verbally (or textually?) say he's open to negotiation? It seems from the recent events in your relationship with him that both of you are totally cool about negotiating stuff. Does he really need to tell you that he's down for that in a text message for you to feel like you can attempt that conversation?
I may be misunderstanding something you said, and if that's the case, please let me know.
Me: Straight male, anarchistic polyamorist, hate labels
N: Straight male, best friend throughout childhood
M: Bisexual female, introduced her to poly
C: Bisexual female, 'girlfriend' of N before poly encouraged de-labeling
A: Straight female, newest in my life
I love them all.