"Enter Pi-hole, a simple and automated solution that works as a DNS resolver and filters on a list of known bad entries that's updated frequently (113,000 blocked entries at time of writing)."

Pi-Hole is not a resolver. It is a forwarder, with only minor differences from dnsmasq.

Chances are, the Pi-Hole user is forwarding her queries to a third party for resolution.

What the Pi-Hole developers call the "Upstream DNS Provider".

The default settings -- the number one suggested choice during setup is to forward queries to a third party DNS service operated by an online ad sales company.

There is no resolver on the Pi-Hole.