It appears this is functionality provided by YouTube themselves where you can set a CNAME: https://support.google.com/a/answer/6214622?hl=en#zippy=%2Co...
$ kdig +tls www.youtube.com @kids.dns0.eu
…
;; QUESTION SECTION:
;; www.youtube.com. IN A
;; ANSWER SECTION:
www.youtube.com. 300 IN CNAME restrictmoderate.youtube.com.
restrictmoderate.youtube.com. 1611 IN A 216.239.38.119