1) Before macOS boots, LittleSnitch ("LS") does not have any ability to block hostnames, e.g: on every boot, any modern Apple product ignores any manually-configured DNS IP and attempts to phone-home
2) Allegedly, this user profile information is stored locally (so LS wouldn't see any outgoing connection attempt to Apple servers)
3) LS does not block DNS-resolution, only IP-connection (i.e. your ISP sees all DNS queries, whether you click `ACCEPT` or `DENY` when LS popup asks)
4) If you're using LS with intentions of primary DNS blockage, you have failed; try pi-hole (or other local hardware DNS resolver); use physically-dedicated hardware (e.g: Raspberry Pi) to run your PiHole, not a Docker/Prox/&c
5) I am investigating another user's comment on using TLS certs to DENY-all DNS, but need to research further on this (new info to me!)