While I agree with most of what you are saying in intent, you did also manage to distort some facts.
The Chrysler alternator is fitted to a few of the Cherokee family, most of them and indeed the bulk of that generation of GA aircraft would use Prestolite kit.
Not the same as automotive.
As for an engineer thinking generator, well yes if he was thinking cars. Very few aircraft had dc generators similar to a car type. Some did, but relatively small numbers. I seem to think some of the Airtourers may have been the latest. They have the cut-out relay normally anyway, fitted to prevent the generator motoring.
The LAME was probably talking about alternators fitted to twins where there is quite a lot of added circuitry, mainly to do with load sharing but which could possibly be damaged by cross-generator starts.
The field current draw is only a few amps, the alternator load on the engine (magnetic) would be minimal also at normal cranking speeds.
It depends on the POH but as we know many will just say you can start with both switches on. Some types like the BN2 don't like you switching the field with the engine running.
The load sharing on the Islanders used to be pretty rudimentary and was easily upset.
The British also have an AD on starters, often an isolate switch or warning light is required.
As for errors in the POH. Yes no doubt there still are some but with email it has never been easier to discuss possible amendments with the manufacturer.
I did exactly that just a couple of months ago with one of the Piper models.
Normally the Chief Pilot would be corresponding with the manufacturer over any concerns in that publication.
They are pretty basic handbooks normally though.
A little like changing fuel tanks at regular intervals to balance the lateral weight distribution.
Most of the Cherokee family have you change tanks once a flight. It is there in the 'Cruise' section. How that becomes the 30 minute fiddle I am not at all sure.
So, yes.. many pilots seem to be operating the aircraft contrary to the POH.