Sedayne's harp tuning is absolutely normal for mediaeval art music, since it gets pure fourths and fifths, and they're the only harmonies used as stable consonances in that idiom. But isn't remotely like what folk instruments like the nyckelharpa use to get built-in pure third sonorities (and what the split frets on Renaissance lutes achieve, and what barbershop singers do).

Let Us Calculate.

Pure major third = 5/4 ratio = 1.2000
Equally tempered major third = 4 ET semitones, 400 cents = 1.2599
Pythagorean major third = 81/64 ratio = 1.2656

That is, if you can't tell the difference between a Pythagorean major third and a just one, you can't tell the difference between just and equally tempered thirds either.