I'm currently a hinge in a V and admittedly, I have some trouble talking about details of me and my girlfriend P's relationship with my boyfriend.
He used to ask a LOT of questions, not because he was insecure or was checking up on me, but because he was so excited for me.
I found it a little overwhelming, to be honest. I'd come back from a date and be asked lots of questions before I even had a chance to sit down - let alone digest it.
So I think I came off as a little cold and uncommunicative at first because I didn't really know what I thought/felt about what was going on in the relationship so I felt put on the spot being asked lots of questions.
I let him know this and he stopped asking so many. I do indulge him sometimes though, when I do know how things are, or when one of us has done something particularly sweet for the other and give him all the juicy details, simply because I know it makes him happy - she's fine with that too, I'm pretty sure they gossip about me whenever my back's turned as well :P
This isn't the same as your situation, but perhaps he doesn't say so much because he's still edging into the relationship and hasn't got everything all sorted out in his head yet. It's still quite early and he may just want to be going with the flow of the new relationship and not over thinking it or reliving everything just after it's happened. It wouldn't mean he was trying to hide anything or keep either of you out, just that he's taking his time to get used to everything - it may take time for him to be merge the different parts of his life together (even just in his head), especially when it's quite new, he'll be doing some adjusting too.