I guess everyone's criteria is different. I don't expect that I or other musicians would always be fooled by a synthetic instrument, but my goal would that be a fairly sophisticated non-musician listener wouldn't be distracted by something not sounding realistic.
I think most would agree with that. As long as it sounds GOOD it really doesn't matter how accurate or authentic it is. Most people aren't gonna be bothered by it unless it sounds bad.
BTW, if my memory serves me correctly I remember playing a few gigs with Gino back in the day. I'm pretty sure he did the Italian Festival circuit and my city had a pretty decent sized one. Played with Al Martino, Vic Damone, Steve Lawrence....back in the late 80's. Good times. Back when it was all live...and full big band's for the backup band.