The confusion seems to be over the difference between "Approved Design Data" and "data approved for use". Approved Design Data must always take precedence. Since even the designers can get it wrong and the regulators, no matter how good, then sometimes fail to pick up the errors, conflicts between documents must occasionally be referred back for double checking.
The following obviously only applies to Boeing aircraft but serves to illustrate the principles involved. On the 'Approved' status of manuals, just go through your Boeing Representative or your usual company channels to ask Customer Support Engineering at BoeCom for yourself to verify this:
On more than one occasion when questioning conflicts such as we are discussing, we told Boeing that we must certify work according to the AMM or the IPC. Their response is always that the AMM and IPC are not approved by the FAA. They are based upon approved data but can only include revised approved data after a significant delay. Only approved data such as Approved Design Drawings can be used for certification purposes. (Note that Tasks such as the test or inspection procedures in the AMM originate in Approved Design "Drawings" although they consist entirely of text)
The operator's regulatory authorities will approve the AMM and IPC for use but that is not the same thing as approving the data contained in them. Approved Design Data originated by the Type Certificate holder and approved by the regulator of the country of manufacture may therefore supersede the information contained in the AMM or IPC.
Once the original Type Certificate is issued, the AMM and other maintenance documents are issued as representing that configuration. Design changes after initial type certification are approved by the FAA as changes to the Type Certificate and introduced onto newly built aircraft by Production Changes such as PRRs or PRRBs for example. These changes may also be issued for post delivery incorporation as Service Bulletins (SB) approved by the FAA. Such SBs contain a statement that they are approved by the FAA and (almost always) cross refer to the original production change number. Airworthiness Directives are issued by the FAA themselves, are applicable equally to both the operator and the manufacturer and thus supersede all other documents. An AD may make an already approved SB mandatory.
As for Aussie Rules Kanga, don't worry too much about the Poo. Although Yanks and Poms do realize that CASA know more about aircraft design than the FAA, many Ozzie LAEs are aware that one of CASA's induction procedures for new staff is to shove a poker firmly up their backsides!
When in doubt, ask the originator and you can't go far wrong.