Hi Tom!
I just duplicated that and you are correct about the tab music being one octave higher than the piano score. This should easily be solvable by the programmers but part of the problem is perhaps that someone at NCH hasn't understood how concert pitch is represented on the guitar and made assumptions that it is the same as the piano (which like many other instruments it isn't).
This is my understanding. On a piano C4 (middle C) in concert pitch is represented by a 'C' note between the treble and bass clefs on a piano. This pitch (piano middle C/C4) is the same pitch (frequency) as the second (B) string first fret on a guitar turned to concert pitch. They are identical. So, anyone who knows music could assume that this is now middle C is represented on a guitar, but it isn't.
Guitar staves are written one octave higher than on a piano. Middle C on a guitar treble clef is written between the 3rd and the 4th lines up whereas on a piano it is written one line below the 1st line. The reason for this is that it makes the guitar staff easier to read (a C note on the 20th fret of the top E-string of a guitar would be represented 7 lines over the top of the treble clef which would make guitar music unreadable - I just opened Piano sonatas vol. 1 by Mozart, for piano, and that rarely goes above the top of the clef at all).
So, all the devs need to do is to ensure that concert pitch middle C is represented one octave lower on guitar tab and shown not as C (5th string/B string 1st fret) but as C (2nd string/A string) 3rd fret AND compensating to represent the lowest notes of the guitar.
It's not possible to transpose either the original score down an octave or the tab down an octave (both of which partly work) because the lowest notes are not recognized by the software as being in the guitar's range so don't appear.
Here's hoping .... especially as this would be really useful for me as well.
Live long and tune well tempered,
Mark