Exactly... you have to find what works for both of you if you're going to have a healthy relationship. Some people are fine with no labels, lots of space, no expectations, etc. For others it makes them feel adrift and confused. There is a happy medium somewhere in there, and you have to find it. Your medium may never line up with his, or you may be able to find one together.
It really is confusing. Like for real. A PTSD relationship is its own kind of animal. It is possible to make it work... You have to make sure you're happy first though. It won't work unless you're happy and secure. Sucking things up to make him happy is just being a martyr. Being a martyr to his PTSD won't ever better the situation.
In the past I probably wouldn't have been happy being in a relationship that was this "loosey-goosey". I'm in a place where it works for me now though. Like we still maintain our own places even though we've been together 6 years and stay together most of the time. He still has that escape hatch open. It makes him feel more secure, and in turn, it doesn't make me feel insecure. We don't call each other "boyfriend/girlfriend" but we're both monogamous. Labels freak him out, but he has no problems with loyalty. I decided that was really more important than saying "my boyfriend this" or "my boyfriend that".
It forces you to reply look at yourself and figure out what YOU need. I'm in my early 40s, divorced, and have two grown kids... so I'm content with my situation. I'm not interested in getting married etc. If I had a different concept of marriage or what a commitment looked like, I probably wouldn't be as comfortable with things. It's all very individual to personalities. I like alone time myself. Also, having been married to a serial cheater previously, as loyal as he is, as long as he is monogamous he can call me anything he wants. I call him my slam-piece most of the time. I don't need the a label... but I could see how somebody would need one in order to feel "official" or to define the perimeters of the relationship.
Not dealing with this stuff is taken for granted in "normal" relationships.