resolver(5) describes the behavior of glibc, not DNS or systemd. Systemd will read resolv.conf if you don't want to configure resolved.conf directly, but that's

resolver(5) describes the behavior of glibc, not DNS or systemd. Systemd will read resolv.conf if you don't want to configure resolved.conf directly, but that's a convenience, not a contract. Dnsmasq also reads resolv.conf for convenience, and puts yet another interpretation on it (which will also break this use case). Both systemd and dnsmasq expect that you'll tell glibc to just ask the local resolver (them).