Curious. Is this based on a personal take or do you know of other guidance on this?
Back when I discussed this topic at several different levels within the FAA, was advised to apply the prevent mx definition to the 43 Appx A(c) list just like applying the definition of a major alteration to the list in Appx A (a). Period. This would have been a big deal for my owner-assist customers to expand their prevent mx capabilities, but unfortunately not all LOIs give direct regulatory relief at the field level. So based on the official discussions I had we stretched the existing prevent mx topics/definition as far as we could while still keeping a foot in the door of Appx A(c) list. And where we couldn't make it work, we looked into an exemption if applicable. Plus in the 10+ years since that LOI I have yet to see any other official movement to change the prevent mx procedures or guidance as mentioned in the LOI either.