They effectively use credentials and cryptography to link the two together in a zero-knowledge type of way. Real issue, although no one is clearly dying for this yet.
Real solution too, but blind credentials and Chaumian signing is equally naive to think it addresses the root issue. Something like Apple will step in to cast a liability shield over all parties and just continue to trap users into the Apple data ecosystem.
The right way to do this is to give the user sovereignty over their identity and usage such that platforms cater to users rather than the middle-men in-between. Harder than what Cloudflare probably wants to truly solve for.
Still, cool article even if a bit lengthy.