I have worked for companies that will receive replacement pages for manufacturer's manuals telling you to destroy the page(s) replaced, I would assume this is fairly common so that you wouldn't accidentally refer to outdated instructions.
Fair enough, I suppose. Businesses do this and they make it perfectly clear in their policies that they do it. For example, "This online manual is updated on a dialy basis" or "Customer feedback is taken into consideration when we update our manual". It's nicely upfront and ethical.
However, the updating that occurs in the Watchtower's publications is not "above board". They continue to state that the "current" copies of earlier publications are actually the original. No where do they inform readers about the revisionism. It creates the worng impression that they have no made mistakes, errors etc.
If secular businesses can be ethically transparent about amendments, updates, etc, I would expect an organization that claims to be blessed by the One True God would adhere to even stricter standards regarding its amendmentsd and updates. They're not and they claim their work vindicates "Jehovah's name".