It's a surface softness.
I got a sample set from USRSA and tried stringing it in the mains with Head PPS 17 crosses.
I was not impressed with the visible notching while stringing it.
PPS is a bit rough. OGSM may have been a better choice.
I hear it plays well, though. (at least in fullbed)
Neos 1000, Eagnas Combo 810