If these engines are prone to shearing the oil like mad then they will likely shear down the 20 weights as well. I'd keep that in mind. The engines in those two UOA's would have likely had an even lower ending viscosity than these 30 weights that sheared.
Because Amsoil (and XOM) made their names on differentiating their products by declaring their basestocks superior. Amsoil trained it's customers to ask "the basestock question" and they should be more straight forward about what they are doing. If a mix of Group III and PAO makes a better oil then they should say so and explain that they've changed their formulations to adopt the best technology.
For $7.30 a quart we should get an "active ingredient" list.