keystring It's not rocket science to count the number of sheet music with the regular grand stave (treble/bass clef) and the one that isn't, It is just a lot of work and this is exactly where AI excells at. I don't know, how exactly "overwhelming" translate into a percentage, but I am quite sure it sits somewhere in the above 90% range. And I totally agree that is impossible to name an exact percentage, because which piece to count, which is a copy of something already counted, and should I count something that is only a slight variation of something counted.
If you don't trust me nor AI, go ahead, take all of your sheet music and tell me how many bars use the regular grand staff (octave shifts included) and how many don't.