I wonder if this is a similar effect as the “classic white marble” impression of Greek & Roman architecture - we have an entire aesthetic (both artistic and cultural) built off of the “purity” of the white marble remains; meanwhile it turns out in their time they were garishly colored and decorated because the Greeks and romans, like all other humans, actually enjoyed living in places and looking at things.
It's quite similar. There's definitely a "white marble effect" coming from the original sources, that tend to be a very barebone notation of the music with basically no indications on how to perform it. But we know from written discussions that creative improvisation was key to performance in that era, and regarded as the very peak of music instruction even more so than composition itself! Sometimes we get lucky and have more detailed sources, that tell us how some pieces might have been performed in detail.
