Yes, battery capacity is the main thing when you compare early EVs. I think the amont of energy the battery can generate and how fast the car can drive a long distance does fit the performance definition, but I agree it’s not the classic definition of comparing the speed on a tiny segment.

On short distances, the 22kWh version is actually a bit faster because the battery is slightly lighter.

It's a dimension of performance, like many others. But lifecycle CO2 footprint is currently the most important performance metric of cars from the holistic pov.