I noticed that Quad 9 is not able to respond to the spy.pet
query:
$ dig spy.pet @9.9.9.9 +short
;; communications error to 9.9.9.9#53: timed out
But Cloudflare DNS is able to do it:
$ dig spy.pet @1.1.1.1 +short
104.26.0.165
104.26.1.165
172.67.74.73
And to be sure, I checked another domain with the same TLD to rule out the option that Quad9 is unable to handle the .pet
TLD, but I received a correct answer…
$ dig hello.pet @9.9.9.9 +short
3.64.163.50
Does Quad9 censor DNS queries?
Nothing is “built into DNS”. DNS is a couple of RFCs that include specifications on how the thing should work. What features one implementation (software) has is decision of those who made it and nothing else.
What you said here is not really on topic, but it is literally part of DNS. I already explained it in my other comment, but here: