I certainly wouldn't patronise a publisher who saw fit to put any such warning in one of Roald Dahl's books.
Tear the page out if you like.
If there was a page with a warning in your book, you can do that. Then you have the book you wanted.
As long as the original is there and a publisher add some silly warning page I really don’t care.
Especially readers' club notes. Even Oprah's.
Then I give the books away when I'm finished. Want to read a book I had? I often edited and sometimes marked it up. That book is a living thing, used and passed around by people.
Or sometimes I throw them away to save everyone else the bother.