Ask someone with headphones and a lanyard in the halls of a datacenter what transport does DNS use, there’s a good chance the answer you’d get back is UDP Port 53.
But not always!
In scenarios where the DNS response is large (beyond 512 bytes) a DNS query will shift over to TCP for delivery.
One prime example of this is DNS NAPTR records used for DNS in roaming scenarios, where the response can quite often be quite large.
If it didn’t move these responses to TCP, you’d run the risk of MTU mismatches dropping DNS. In that half of my life has been spent debugging DNS issues, and the other half of my life debugging MTU issues, if I had MTU and DNS issues together, I’d be looking for a career change…