I think you are misreading his comment. He is saying that on a VPN it is standard behavior that if you visit site A and site B they will both see you connecting from the same IP and can infer you are potentially the same person.

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fragmede an hour ago | parent [-]

Site A and B have to collude in order to make that inference. Outside of Cloudflare, no one is colluding at that level.

	▲	antonvs 34 minutes ago \| parent [-]
		That would only be true if there were no ad networks. But today’s internet is essentially a giant ad network.