It’s all relative. It allows it to spin more easily than a standard, non multi-grade oil of a given viscosity rating AT THOSE EXACT TEMPS.
Again:
5 @ cold = 5W30 @ cold
I just don’t get where you see an inconsistency. The first number is what the VI additive allows it to flow like when cold. It only affects the cold temp rating. All it’s saying is WHEN I’M COLD, I SPIN EASIER THAN I WOULD WITHOUT AN ADDITIVE. This DOES NOT mean that the oil is THINNER @ 32* – just that it’s thinner than it would be without the additive @ 32*.