I think it is overdone. At the top of the 337 form, it says for major alterations. Then go read the far part 1 definition of major alteration.
“14 CFR Part 1.1
Major alteration means an alteration not listed in the aircraft, aircraft engine, or propeller specifications -
(1) That might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or
(2) That is not done according to accepted practices or cannot be done by elementary operations.
Minor alteration means an alteration other than a major alteration.””
I get the STC changes the type certificate of their plane and it it should be documented, but the installing mechanic decides whether it’s major or minor. Not the person who made the Rosen sunvisors. To install the ADSB wingtip Beacon you fit the unit in place of the removed NAV light assembly. You not change any holes or even hardware.
Anyway that letter from their regional Counsel explains it just the same