Coolerman,
Please keep in mind that the posts on this, or any other board, are simply opinion. Some may be based on the poster’s interpretation of data or long personal experience but they are still opinions.
To take what people post as a personnel affront does not make your point less valid or theirs more important.
The object is to give your views in hope that the OPs that are asking the question will find them of some value.
The fact that there are many, sometime very different, approaches to a problem is simply human nature.
In my opinion the manufacturers feel that there is really no incentive to spend large sums on a detailed manual that few will read; especially if the customer making the repairs themselves voids the warrantee. They feel it is best to return it to the factory or dealer where they have some control over the repair results.
It is frustrating for those handy people with older units, but it is not likely to change.