@Berzelius: I'm loathe to change a menu item that has been there since the beginning, and OTOH, I'm not finding a potentially better *concise* wording of what it does... :/
@khromosone: Which
exact Kindle device are you using? If your device block is accurate, you'll need a jailbroken device and another tool on device to apply the changes (I'd recommend LibrarianSync), cf. the first post.
You also seem to be following deprecated instructions... Follow the first post, and what the actual UI of the plugin tells you to do, not anything else, it's smart enough to point you in the right direction depending on your device.