MacOS Resolution of localhost

It seem like this is, in fact, hardcoded in mDNSResponder.

╰─ grep -A5 -B5 "Register localhost" ./mDNSResponder-1096.40.7/mDNSMacOSX/mDNSMacOSX.c
        const domainname *const localHostName     = (const domainname *) "\x9" "localhost";
        const domainname *const broadcastHostName = (const domainname *) "\xd" "broadcasthost";
        const mDNSv4Addr        localHostV4       = { { 127, 0, 0, 1 } };
        mDNSv6Addr              localHostV6;
        // Register localhost 127.0.0.1 A record.
        RegisterLocalOnlyARecord(localHostName, &localHostV4);
        // Register broadcasthost 255.255.255.255 A record.
--
--
        // Register broadcasthost 255.255.255.255 A record.
        RegisterLocalOnlyARecord(broadcastHostName, &onesIPv4Addr);
        // Register localhost ::1 AAAA record.
        mDNSPlatformMemZero(&localHostV6, sizeof(localHostV6));
        localHostV6.b[15] = 1;
        RegisterLocalOnlyAAAARecord(localHostName, &localHostV6);
    }