jcjeant;
Yes, the pitch change towards ND from 15deg NU would not be brisk, that's for sure, but with no Nose-Up input, the nose itself would slowly, (languidly) drop, probably not very far but it wouldn't be in positive territory, (I recognize that you are including the THS 13.6deg NU position as having an effect - I leave that to the aeronautical engineer people).
Also, I'm considering that "letting go" would not be a sustained response (I would hope!), but a momentary action if indeed he had to re-establish "neutral". But in fact, the neutral position of the stick is abundantly felt and is not at all a problem to place, so practically speaking, the entire scenario posited, (unbelted, finding neutral on the stick) is not plausible.
HN39, thank you. I'm likely a bit provincial in my awareness of these things!