> Facebook are explicitly not allowed to farm for PII, so unless they have explicit consent

And for the past 8 years Facebook has been fighting this in courts and kept collecting every scrap of data they could get their hands on

> Therefore its unreasonable for them to guarantee them they will never process your data when submitted by a third party.

No, it's not unreasonable. They wouldn't be in this situation if they didn't opt everyone by default in the first place. They very explicitly looked at your "not allowed to farm for PII", said "fuck it, we have deep pockets and lawyers" and literally opted every one into PII farming.

> If you can design a way to stop people's data being processed when uploaded by a third party, I want in on that.

Don't farm it in the first place. Don't opt-in everyone by default into your PII farming machine.

It's also funny how you went from "AI people have no access to user data" to "oh they cannot guarantee user data for people who explicitly opted-out won't end up in the models"