Not quite, the viscosity index of an oil is Kinematic Viscosity, KV40 and KV100, and essentially the slope of the line between them.
From the early days of multigrades, it was found that (some) oils didn't live up to their KV promise, and some clever people started researching what happens to these oils inside engines...they found that these VII polymers start to get stretched/aligned in areas of the engine where the shear rate is very high (e.g. in the loaded zone of a bearing), and developed HTHS as a measure, and started including that in J300....note that the early 0W, 5W, and 10W 40s only had a minimum HTHS of 2.9, making them about as useful as a 30 grade.
Less use actually, as for similar protection, their KVs were much higher than they needed to be...
I'll explain...Newtonian fluids, like straight grades produce the same viscosity at all shear rates...the viscosity of the oil as it flows to the pick-up, through the galleries, and through the bearings doesn't change. And for reference, an SAE30 will have an HTHS of around 3.5, which is the minimum (now) for 0W, 5W, and 10W 40s.
Polymer thickened oils have a varying viscosity depending on shear rate.

That curve on the right shows what's happening to the reference oils as they are run through the engine bearings at varying RPM...once the shear rate reaches the point that the polymers are flattened out, it maintains that viscosity...called the second Newtonian range.
So you can see in the chart on the left, that the "multigrade" oil had a viscosity of 9.2cst t low shear rates, and 6.7 at high shear rates...it will flow to the pickup as 'though it's a 9.2, and protect the bearings as 'though it's a 6.7.
And that's what the MRV and CCS are doing...the former is the ability of the oil to flow to the pickup, and up the suction pipe, and the latter what happens in the bearings.
Here's an (old) J300

Take the 0W range, 6,200CP CCS at -35C. A Newtonian oil would be expected to roughly double the viscosity (12,400ish) going to -40C, but the standard allows it to "thicken" nearly 10 fold.
IMO, as the VIIs are bolstering the low shear rate viscosities, and the standard needs to allow for that.