The simplicity of IV validity quickly disappears with nuances. see But, a more important aspect of the "repackaging" is CREDIBILITY, namely, judgments are recruited from where they reside, not from where they are distorted to appease the identifier.
Consider the IV validity again, and ask yourself "what judgements were necessary to execute this exercise?". Mark them. Now compare to the judgments required in the PO framework, which are cast in ignorability language, (See Angrist etal). Finally, ask "What type of judgments
would be more CREDIBLE if I were the one to make them?" I am sure your assessment of the value of "repackaging" will become one of greater appreciation, perhaps even one of necessity. #Bookofwhy