Latest electronically controlled variable displacement oil pumps can deliver just a right volume of oil and pressure using lighter weights. Is it likely that use of heavier oil instead of recommended 0W-16 can have a negative effect on variable valve timing actuators causing them to be sluggish which could possibly affect drivability, performance and engine longevity? I don't know.
The engineers and drivers in Japan could answer that, since 0W-16 oil has been used there for almost two decades.
Going thin is the direction of lubricants development. Even VW 508/509 all approved oils are only 0W-20.
I looked at PDS (in Japanese) of TOYOTA GENUINE MOTOR OIL SP 0W-16 GF-6B blended by Exxon Mobil, Ravenol EFE, Valvoline Advanced FS, Motul HYBRID, Amsoil OES and HPL.
Pennzoil makes Platinum 0W-16 but PDS is not available.
Here are the properties of the oils.
As you can see, the percentage content of VII (Viscosity Modifiers) is quite low and this would suggest that the oils are very shear stable even though they are thin.
Still not enough of data like, mileage and time with those thin oils in US to conclude if there's any harm to engine as far as wear or all will be good. I suspect the later is correct.
I would definitely trust the engineers and automakers recommendation based on a rigorous approval process and testing backed by R&D with big budgets over someone telling me to go thicker because they did and no harm is done and makes them sleep better