Is Congress acting smart on plug-in hybrid tax credits?

Only about battery capacity, not actual EV range, nor real world fuel economy?

The Senate has passed a new tax bill that will provide tax credits for plug-in hybrid vehicles ranging from $2,500 - $7,500, depending on the vehicle's battery capacity. To be eligible for the credit, such plug-in vehicles must store at least 6 kWh's of electricity.

So, battery capacity, not actual EV range nor real world fuel economy, is how Congress judges plug-in quality? Does that really make sense?

Finish: $7,500 plug-in hybrid tax credit passes Senate - Too favorable to Volt?