No way MacOS parse tls clienthello looking for SNI.
Also I doubt a DNS resolver runs in the Mac kernel, ring 0 to pull this off.
The thing with DNS is that it works on layer 3. Hold on, what? Yes, layer 3 because you obtain network address for layer 3 (ip4, ipv6) but latency can be measured only in layer4 (tcp, quic). Of course I know that common wisdom says DNS is a layer 7 but from functional perspective, you are yet to establish your destination network address, therefore functionally it's like layer 3 to me. Or even lower, because without destination, you can't even start creating a packet and inspecting your routing table entries figuring out if you can even reach it ;)
There is zero chance Mac resolver libraries can connect you to the fastest responding server - unless there is no Berkeley sockets but something that allows you to do a connect(char * fqdn) and system library return you two pipes, one for write, other for read, and that you can close them independently. I doubt it there is such a thing, but don't know Mac os API.