In my opinion, using the four-ball test seems to have as much relevance as the test one of the chlorinated lubes (I believe it was Duralube) demonstrated in an infomercial, showing its lube preventing a cutoff tool from cutting a workpiece mounted in a running metal lathe. Car engines don't use "knife bearings". Nor do they use any kind of ball arrangement under extreme pressure on a rotating shaft.
Not trashing Amsoil, but for most buyers and users a true comparison test in real engines over many thousands of miles against a large sampling of other brands would be far, far more useful.