It's not imagery, it's innuendo. I know that's splitting hairs but they are important hairs to split. Without trying to get too hyperbolic this discussion could be likened to the 1964 Supreme Court debate on pornography. The phrase "I know it when I see it." as spoken by Justice Stewart at the time actually was his dismissal of the material in question as being pornographic. (People often take that quote out of context and use it erroneously.)
So while the book in question is unseemly, creepy and downright crude that doesn't automatically make it pornographic; it doesn't automatically violate the CCPG.
*To be fair I'm not interested in defending this particular book as I find it ridiculous trash, but the underlying abstract question of what is and what isn't pornographic is an interesting topic to examine. I doubt Hugh intended for this to devolve into a study on ethics but nonetheless here we are. His original post makes for a valid and interesting debate on this subject (as long as all parties can be civil and not try to play the game of one upmanship by implying others are perverts by even discussing the topic. )
As someone with an analytical mind it seems like something you'd be interested in JL. Although to be fair I know that this isn't the intellectual hill that I want to die on so I won't blame you for not taking the ball and running with it.
My thought is not that it is imagery but rather the "other content" part of the rule. It may not be literally said type of imagery but the context of the dialog and such is VERY suggestive and with it having the look of a children's book we are in really creepy territory.