And frankly, seems like I see this test come up on all kinds of builds, and most of the time nobody even asks what the motor is before they start trumpeting how worthless this or that is using this test. Look at the reference I linked in my first response, the question was if the 340 manifolds would fit in a chassis and no one asked what motor he was building before bringing up this test and telling the OP they weren't worth trying to fit.
I'm not the one that has to validate anything. If you want to apply it to a broad range of motors, you are the one that needs to show that it can be applicable. I'm saying is too narrow focused to be useful for anything beyond a stock 5.9.
I will say that the video from Nick's Garage seems more useful to me than the HR magazine test, but I haven't watched it all and I get the impression some don't trust Nick or something. But from what I've seen so far, it must have a bigger cam than the broomstick the stock 5.9 has since it appears to peak 1400 or so RPM higher.
No argument beyond my opinion that most times that I see the manifold test put up, it is taken with a huge grain of sugar instead of salt.