That’s not quite correct. To perfectly preserve, you’d also need to change the string thickness, tension and weight, which may involve a change of materials, and may not even be possible to retain proportionality between strings. You’d have to change the body of the guitar as well.
I have no idea which is further from a purely pitch adjusted version of the original! The key (no pun intended) takeaway is that virtually all instruments sound different in each key, and just playing higher will sound different to eg recording and adjusting the pitch digitally (or analog-ly).
Oh, you are about timbre. Sure capo can't change that.
> That's because you are using a guitar, which is not perfectly in tune no matter how you tune it.
I've though powersnail point is about different shapes and your comment is about True Temperament guitar [1], [2].
Do you think timbre is the reason we notice pitch changes? And we would not notice transposition if it was pure sine? I am sure going to test it [3] and will add pure sine instrument.