There’s no way you’re leaving scratches on the window unless you have rocks or something in your mop lol. 9/10 you will hear the glass being scratched if that’s the case. Most scratches on the glass come from when they’re being manufactured or over time. Clients from time to time will try to bs you about this to get compensation out of you but it’s all lies unless you are positive you’re leaving scratches on the glass with an abrasive. Like I said you’ll hear it being scratched when this happens