In the context of my question in his AMA.

Since the service is paid, all queries require a token that is associated to the payment. Obviously I used LN to pay but most people will use credit cards.

He said they have no incentive to sell data and that appears to be sufficient to him. The point is that we just have to trust them on that. All trust, no verification. Having a blinded token scheme or ecash system one could prove funds but without linking it to the actual payment.