This is interesting because CIPA doesn't require (to my knowledge) that websites used to circumvent filtering be blocked, only that porn, child abuse images, and content harmful to minors be blocked. Translation services are not pornographic or harmful.

Correct.

However, the law itself is written as a "min", not a "max" - i.e., it says itself that more blacklisting is fine. There doesn't seem to be much interest in making a legal challenge on the topic, after the ultimate loss of the previous CIPA case.