In mechanical systems, it doesn't matter if you make the strongest parts stronger, when the weakest part in the system is always going to limit the performance. A solid lifter, pushrod engine depends on good oil for the cam and lifters. It makes sense to tailor your oil needs to where its' performance is most critical... and of course that's the aspect you need to test to make sure the oil you chose performs as needed...
It's always sad when ludites or wanna-be experts publically undermine good research with their long held misconceptions or single data point opinions. They can cause a wave of false beliefs that can go forward as fact when repeated enough. I recall 30 years ago a norton expert I knew saying that my '70 cases were thinner and more flexible than later model cases which helped them keep from breaking when the crankshaft flexed at high RPM... I probably believe him for a while, then came to my senses...
It seems to me that Jim's testing made sense, and he didn't claim anything beyond what his testing showed. In the end, if there's some unaccounted factor that negates his findings in real engine usage, he's already admitted that possibility which is a sign of keeping an open mind towards the results of the test.
!!) is it worst than the 20w60 of the same brand ??????