This is correct; what people fundamentally misunderstand is that data brokers directly sell personal information about people, but Google and Facebook only allow for targeted advertising while keeping personal information within the confines of their company.
This isn't misunderstood, just not relevant. Google sells to a funnel that plays a numbers game, not for individuals to be targeted.
The meta-conspiracy-theory would be that the dossier industry whips up conspiracy theories about online advertisers in order to maintain their own low profile.