Regardless of the EPA, engine engineering and oil formulation as well as viscosity go hand in hand.
There are many valid reasons for running different viscosities, but “because x viscosity is like water” or because “grand pappy ran 60w in his hot rodded Ford Flathead” are not objective...
So many people going against manufacturer recommended oil viscosities just because they “feel” the recommended oil is too thin because they do occasional autocross or track days.
I’ll start by saying I have no problem with anyone using whatever oil or other products they want in their vehicle...