It is a fine line between what is actually legally required and what is recommended or interpreted as being required.
Case in point is the Slick 500hr inspection. On, for instance, the PA28-161 there is no call up for a 500hr inspection. Slick has a Service Bulletin to say that a 500hr inspection must be carried out but that is not mandatory as it is only a SB. LAMP leaves it to the discretion of the CRS signatory to determine what should be carried out to ensure the safe continued operation of the aircraft when it comes to continuing airworthiness stuff - like maufacturers SBs.
Normally, mags fail shortly after a 500hr inspection has been carried out....
PS If the prop on the aircraft in question actually had AWN75 carried out 100hrs ago, with the hours that it apprently flies annually, one would have thought the owner would have been better advised to bring the overhaul date forwards that few months....