I really doubt Toyota would stack their reputation for reliability on a minor improvement in MPG. I think it's safe to say that if Mr. T recommends a certain oil in the manual, it's tested and proven. It won't fail just outside of warranty.
When in doubt, go with the grade in the owner's manual. Sounds like @suprarx7nut is all over the place with grades (but tests it), and I imagine would have made a deal of it if any of the Blackstone reports came back worse than others.
It's not just Toyota - it's an entire industry. Like it or not cars are becoming more disposable every year, a trend in which Japan has been a leader. That 2019 RAV4 on 0w-16 has an EPA rating of 26 / 35, which is just outstanding, but there was a trade-off there.