OK but if that "known good" DNS server goes down or isn't available, you still have others you can fall back to. The device shouldn't just become completely useless. But that's what Google is doing here. It's their DNS servers or none, it seems.
On one hand it feels wrong to not ask in parallel.
On the other, $%#@%#$%!$@# the %$#%#$%^$#@%#$! packet filters that block DNS packets to everyone except the local brain-damaged resolver. Or even redirect. If Google will fight that fight I'll happily enjoy the benefits.
In my haphazard experience, the networks that block access to UDP port 53 are more than likely to have gelded broken name servers that e.g. serve empty NXERROR results for anything but A/TXT, and receptionists that say, "uh, let me check" and then check that their browser can open the google home page. (Insert invectives here.)
I've seen be fixed. Once. One meeting I attended started with a quite broken network, but it was an IETF meeting, and the IETF tools team reconfigured the AP channel layout, the DHCP server and the caching name server at that hotel and after that it was fine.
Evidently, they are:
https://en.wikipedia.org/wiki/DNS_over_HTTPS
https://developers.google.com/speed/public-dns/docs/dns-over...
Curse it all you want, but forcing all DNS lookups to be resolved by a particular server is often an important security measure.
Don't like it? Use TLS and verify certificates.