If he gave them the docs he certainly has on this stuff, and said "i am glad to sit down and walk you through any other answers or questions you may have", they'd be fine with it as an initial response.

I think you have pretty much already assigned a negative agenda to NHTSA, when they've just requested some info.

While they may have followups if they don't like the answers they get, of all the agencies you find, NHTSA is not one that tends to have a serious pre-bias towards anyone.