The default is not for this to respond in a way that disables changing your DNS server, therefore they're changing the default without asking.

Notice that you could do this the other way: Query a value in the existing (local) DNS or DHCP that not only allows you to enable DoH but also specify which server all the local devices should use. Then if the DNS server chosen by the local administrator/user supports DoH, it could respond by saying so and you could use the protocol without changing your DNS server. But that's not how they did it.