Is he hiding something?

So we have been dating for 3, known him for 7 months now. We have a very healthy relationship and i do trust him however, last night i started questioning some of his actions. We were having a laugh and I was going to show him something so I asked for his phone password (which I never have before) and he said i’ll unlock for you. So i asked, out of curiosity, what his password was just to see if he would give it or nor as there has been times where he would go on mine to change music etc so he knows my password. So we had a conversation and he said that he believed we should have some sort of privacy and that he feels that phone is part of it. I said I respect his decision however, me knowing his phone password does not mean invading privacy. Just because I know his password does not mean I will ever go on his phone without him knowing to purposely invade his privacy. I told him I found is bizarre and gave a simple example such as him driving, me wanting to change the music and instead of doing it myself having to give the phone to him so he can unlock it…

I understand where he is coming from and agree that just because you are in a relationship does not mean you should have zero privacy however, when I made it clear that i will also change my password and have my own privacy he did not like that. He wants to know my password but I should not know his? Bizarre. So I changed my password when I got home. I did not react and we discussed this in a very mature way and I know this conversation will come up again when he realised I changed my password. Any ideas on what I should do?