I just answered my own question with a quick bit of googling on modifying systemd's resolv.conf records. https://www.freedesktop.org/software/systemd/man/systemd-resolved.service.html#/etc/resolv.conf
so it is a systemd thing to use 127.0.0.53, ok.
I had someone pull request a little bit of info about updating systemd DNS into my readme here in case you missed it: https://github.com/diginc/docker-pi-hole/pull/181/files
If you perfer to leave systemd DNS on the first link I sent documents customizing the servers early on in the page:
The DNS servers contacted are determined from the global settings in /etc/systemd/resolved.conf, the per-link static settings in /etc/systemd/network/*.network files, the per-link dynamic settings received over DHCP and any DNS server information made available by other system services. See resolved.conf(5) and systemd.network(5) for details about systemd's own configuration files for DNS servers. To improve compatibility, /etc/resolv.conf is read in order to discover configured system DNS servers, but only if it is not a symlink to /run/systemd/resolve/resolv.conf (see below).