I feel like you're veering dangerously close to victim blaming here. Them asking the customer to erase their devices to "protect their data" seems like a thinly veiled attempt to cover their asses if one of their apparently not well vetted technicians decide to violate somebody's privacy illegally. It also sounds like a major pain in the ass especially for people who don't own a computer to backup that data to.
I have no sympathy for Apple here especially considering the level of FUD they spread about the Right to Repair movement exposing your Apple device to allegedly dangerous third party technicians.