So wouldn’t it be reasonable to test what happens when it can’t reach its upstream servers? I assume Russia will need to provide some way of DNS record changes still working. It could be they intercept/replace 8.8.8.8, or they intercept the upstreams, but whatever it is I can see why they would want to test it first.

Not that I agree with the ultimate reasons for doing this exercise — mass filtering and surveillance — just speaking to the technical merits of why a test would be done.