Oh yes, the ever present "coal powered car" argument. ZZZZZZZZZZZZZ
For the EV they want to look at emissions from the plant to the wheels. For an ICE car they want to look at the emissions from the tank to the wheels. Plant does not equal tank, and what they claim is an "apples to apples" comparison is more like an "apples to potatoes" comparison.
If you really want to do an "apples to apples" comparison then, if want to go all the way back to the electrical plant for an EV, you have to go all the way back to the refinery for an ICE vehicle. When you do that you find that it takes quite a bit of electricity to just refine a gallon of oil. Nissan says 7.5 kWh. The DOE says 6 kWh. This is the amount used, not the amount of electricity produced before transmission and distribution losses. If transmission is 93% efficient then it takes 6.5 kWh or 8 kWh at the plant just to refine a gallon.
But of course it doesn't stop there. Once a gallon of gas is refined it has to be stored and delivered. That takes more energy and involves more emissions. Once the electrons have been captured by the battery that's it -- no energy is expended and no emissions are created.
IOW for a Prius to go 50 miles it needs one gallon of gas and at least 8 kWh of electricity. A Leaf can go the same distance using, at most, 17 kWh of electricity. Even forgetting that the Leaf in a place like CA with a relatively clean grid will emit far less of every pollutant and emission than a Prius even if you don't count the kWh needed to produce the gallon of gas, once you do count the electricity needed to produce the gallon of gas the Leaf will emit less and pollute less even if it runs on electricity which comes exclusively from coal fired plants.
Not to mention that the "green" index doubtless only looks at CO2, as if all other emissions and pollutants don't matter.