While they never said they wouldn't hand it over to a steward, it also requires MORE work on their part to vet any strangers to ensure they are not there to abuse the system.

Handing it over to another public ad-blocking DNS resolver might be reasonable, but I think it's more honest to disable to service to let users know (in spectacularly failing way, true) that this particular service is going offline (basically, don't transfer the data to a service these customers have not signed up for).

Since it's DNS, they could also just resolve everything to their own homepage saying the service is dead, but that would still break a bunch of non-web-browser apps.