It is difficult to draw up hard and fast rules.
For example the mfg maint list for my Socata TB20 is as long as your arm, and contains loads of stuff which is patently unnecessary, like dismantling the emergency gear release valve every 2 or 3 years. There are no apparently lifed parts in that valve (the o-ring seals will last decades) and the job is a real pig, taking a whole day (the LH seat has to come out to be able to climb in there) and IME most mechanics do it wrongly and eventually the threads get chewed up and then you are looking at 4 digits for a whole new valve which is a French made custom machined part. There is also no apparent failure mechanism because the valve contains just one long pin, whose mere sliding movement does the "job" of internally bleeding the pressure, and one can just check that it slides OK every once in a while. As a result, on an N-reg, you don't mess with that valve, and this is not only 100% legal but is also sensible in objective engineering terms.
The underlying issue is that the mfg who compiles the list has an obvious financial interest in making it as long as your arm
Also European manufacturers tend be be "European minded" and they tend to throw in everything including the kitchen sink.
I maintain my TB20 on a money no object basis but I don't replace stuff for the fun of it...
But somehow one has to reconcile this with the reality of aircraft maintenance which is that many/most MOs tick all the boxes but only do what they think is worth doing, or what they can be bothered to do in the less honest instances.
What the regulators no doubt see is occassional maintenance lapses and they think that by being ultra prescriptive they can fix that. But they can't. That will never change.
Ultimately one has to accept that GA is less safe than CAT, for various reasons, and most of them are nothing to do with maintenance anyway (which is just as well since CAT is also maintained by humans
).
Regarding ICAs, the FAA is getting quite picky now to make sure every 337d mod has an ICA section. In most cases (avionics) there is nothing to do there, but I am sure an aftermarket turbocharger might have specific instructions