My guess is this is just incompetence and not intentionally made to block CloudFlare.
I have one of those routers, and I couldn't use 1.1.1.1 because it was routing to an internal interface on the router. I confirmed this with ping, I was getting microsecond response times from 1.1.1.1.
Under the new firmware, 1.1.1.1 is just dead. So it's probably still connected to the local interface, and nothing is listening.
Probably because they know they would never be able to convince anyone that it was a technical bug and not malice. A surprising number of people seem to be convinced this was unintentional.
I have one of those routers, and I couldn't use 1.1.1.1 because it was routing to an internal interface on the router. I confirmed this with ping, I was getting microsecond response times from 1.1.1.1.
Under the new firmware, 1.1.1.1 is just dead. So it's probably still connected to the local interface, and nothing is listening.