If you give people specifics, they can argue about those specifics. Handwavy "crt" claims are all most people need to support this decision. Digging in to actual facts and specifics gets too messy, and might cause people to have to think too much.

They do not want to jeopardize this moral panic they've crafted by showing people concrete examples of what it's all about.

Indeed, even the names of the books are not released.