I mean, yeah. Maybe I'm being naïve here but in your scenario by simply just telling the police exactly that story, when she was first reported missing by her parents, would be a huge help in at least narrowing down where she was.I don’t know. Is it suspicious? Sure, but even if he didn’t kill her it probably shouldn’t talk to the police without his attorney/doing it for him.
Let’s say what actually happened was that they were both fighting and thought it would be miserable driving back together so he dropped her off in a nearby town so she could rent a car and they could drive back separately (I don’t think this happened, but just as an example). In that case, would talking to the police even be helpful at this point?
And to be clear, I am not saying he wasn't in his right to hire an attorney or that he shouldn't have, but to not provide any insight or information at all to help with her whereabouts is what I find it most suspicious.
Say in that scenario Maybe they had a huge fight and were on their way to getting a divorce. You think he still wouldn't have any worry if she was okay, and want to try and help find her?