It appears this particular directive applies to only those 8 specific sub-assemblies with the noted serial numbers.
My educated guess would be that there was a bad batch of some unserialized component (think a bolt or the literal unobtanium rubber seal) that they identified, but could only attach to a window of use, and X months of thingy use in a repair bay means touching those 8 assemblies.
All normal aviation things. Nothing to see here.