What is your opinion on this behavior?

I'm dating someone, and somehow we never have deep conversations. He always says I can talk about anything I want and I can ask him anything I want, but when he starts conversations, the topics are always superficial, and I usually get the feeling he's not comfortable with deep things. He never initiates deep conversations and only asks superficial questions.

Once, we had a slightly deeper conversation in which we had different views, and we were discussing this matter. At some point, he just got up and left. If I'd known, I would have ended the conversation early, but he left suddenly. I wasn't expecting it because we hadn't been arguing. Afterward, he wrote that he wasn't comfortable with this sort of thing, and that he had his opinion and I had my opinion, and that we should just leave it at that.

When I brought up another profound topic two weeks later, he did say a few things about it, but when I responded, he told me to drop it and that he wouldn't say anything more about the topic, that I was totally exaggerating and overthinking things. To be honest, I had criticized him a bit on this one, but without being offensive, just matter-of-fact. He also said ironically, "Thanks for saying that."

I think I'm also difficult at times because I like to talk/discuss topics, but I've never experienced someone blocking everything out as quickly as he does.