I believe he's arguing against the idea that Apple won't implement this device sharing because they don't want to sell only one device per family.

Because he is not replying to GP, he is replying to the parent:

> Every Apple device, from Macbooks to iPads to iPhones to Airpods is built to be a personal device. (...) Apple doesn’t want to sell one shared device to a family. They want to sell multiple devices to every family member.

Not sure why people are having problem understanding that.