https://bugs.winehq.org/show_bug.cgi?id=54818
--- Comment #3 from Hans Leidekker hans@meelstraat.net --- (In reply to François Gouget from comment #2)
It gets its configuration from the same DHCP server. So its "Primary DNS suffix" setting (and also "Connection-specific DNS Suffix" and "DNS Suffix earch List" in the ipconfig output) matches the "domain" and "search" lines of the Debian machine's /etc/resolv.conf file.
Right, otherwise Windows can't be expected to try wpad.my.domain. Perhaps something else is needed to trigger proxy URL detection, or perhaps it shouldn't be reported in this case as you suggested.