I’ve edited my post above, not sure if you caught that.
I know that straight oil such as just “30” will be the same at high temp at 5w30, as a straight oil has only been tested at operating temp. That won’t be confusing anybody.
Is there a different between SAE thickness rating and being “physically thicker”?
Because then I’m still just as confused. If low number is indeed thin and high number is indeed thick, and one oil rated 0w30 (for example) is going to be thin like 0 at 32deg and thick like 30 at operating temp, that would imply that it gets thicker as it gets warmer.