Hi,
I have a router which manages VPN connection for all clients (PI hole's as well). VPN's DNS pull is disabled by default (push "dhcp-option DNS piholeIP"). Router's default DNS server is Pi-hole.
PI hole's default DNS server is set to Google. However when I check for dns leaks I can see only my VPN provider's IP but not Google's.
On the other hand, when I set up DNS servers manually in PI-hole's control panel, I can see the manual servers when i'm doing a DNS leak tests w/o VPN servers IP.