What Marc said 
Good to know-I’d played with that slider in the past but always have left it as New but my latest work perhaps sounds a touch better with it at 0.15? I’ll have to try that setting (.15) the next time I’m composing a work with piano. Thanks!
Their notion of worn out includes being a bot out of tune, but you can have a worn piano tuned exactly. So its a bit simpolistics= what they do, with the model parameters they have. nevertheless its a really interesting setting and it can take the edge of that ‘new out of the box’ sound.
Perhaps this topic would be better on the Pianoteq forum - because it’s going to get very long, clearly, and it’s not related to my query, which probably should have been on that forum to start with.
If you are interested, here is an example of a more traditional piece. I found the score on the internet and loaded it in Dorico. The piano is Pianoteq. But it is placed in MIR.