Steinway wrote:... My wife did note that the top 10 notes on most samples were slightly out of tune!!!!
I'd be very curious if she senses the tones too low or too high!
You had a Boston/Steinway grand which will certainly have been stretch-tuned, yet maybe less than an upright piano: A note an octave above the other is not exactly double the frequency as you would expect by calculating. Moreover, the diametre of the bass strings will make the first upper harmonic resonate at a slightly higher frequency than the double and so on. So, in order to get a purer sounding octave and avoid beating (interferences) if you play an octave with your fingers, the higher notes are also tuned a little big higher. In the middle range, there is so little strech that you won't hear it, but on the lower and upper end, you might notice it.
The larger the size of a grand, the slimmer you can have the bass strings if they are meant to sound good. And the slimmer the bass strings are, the less you need to stretch the tuning to compensate that effect (depending on the thickness of the chords). Which may be why concert grands are longer: They can have the better tuning.
I don't have any idea if Nord includes stretch-tuning into their (XL) piano samples. If they do, your wife should hear a discernable difference between the stretching of the upright pianos and the grands - namely the larger grands should sound "better": Grand Lady D, Concert Grand, Bösendorfer e.a. As your wife's ears may be used to stretched tuning, it would be interesting if she'd consider the upper notes too high or too low - which could be an answer to that do-they-stretch-question, if used in XL format.
I still haven't tested that as I'm not used to play on a well tuned piano - I even dislike them a bit. You might want to have a look into that conversation: nord-piano-grand-forum-f10/nord-piano-samples-out-of-tune-t7776.html?hilit=stretch%20tune#p49380