The additive package is really what dictates the wear numbers, the base oil is just there to provide the viscosity and resist breakdown. PAO is more of a PITA to blend with because it requires something else to offset it being hard on/shrinking seals, which is typically POE, which is also expensive. So ultimately, the combo ends up being more expensive. Of course the advantage is better oxidation resistance and better cold temperature performance. Also, the slate of PAO base viscosities is extremely broad, which is why I think M1 EP 0w-20 is basically a monograde with its VI of 131. Mobil has likely used a blend of PAO bases to hit the target visc and using POE and maybe some AN's to aide in solvency and seal compatibility.
It's probably the most visc stable 0w-20 on the market, it's also probably one of Mobil's most expensive oils to blend. But since they are so vertically integrated, that's likely not a big factor in the total scheme of things.