I would suggest that you never deviate from what is stated in your manual in any way.Please advise what you perceive as baseless or I can't really engage in meaningful conversation.
It is 100 percent factual that engine replacements are almost always approved by the regional tech from the manufacturer. I assume you concede that certainly dealerships don't approve them.
Fact 2 is in an engine replacement it is almost certain the manufacturer will require a record of all required maintenances. I assume you are not arguing that?
So apparently you are arguing that a regional tech would not decline a warranty claim if you used a non recommend oil is that correct?
Do you have any evidence to support that odd conclusion?
I know if I want to deviate from requirements I always email the manufacturer and they will tell you if it impacts the warranty. Do you have something like that in writing that they would be approving claims for you if you use a non recommended oil?
The fact remains that in the case of 504 00 oil in my VW as opposed to 508 00 the engine is protected better and therefore helps to preclude and prevent a warranty claim.