Docker windows now support host networking. I was thinking that using this config instead of bridge mode could help to get visibility on the client name doing a DNS query instead of getting only localhost.
I started the container with this setting, pihole container is accessible through localhost or server IP directly and working properly. But it's not resolving the client name issue.
When I last checked about 3 days ago, Docker's docs still stated that to be available only as part of the beta?
I'm not using Docker Desktop for Windows myself, but from what I gather, I think its possible that NATting may be imposed by the virtualisation in Windows rather than by Docker's network mode.
That's a fair bit of speculation on my behalf, and you absolutely want to verify that with Docker/Windows experts, hence rdwebdesign's advice to consult Docker's forums about this.