That's not what they're advocating for, they're saying a plugin hybrid with a 75 mile electric range, that uses a fossil fuel engine for more range.

The general idea is, suppose you want a vehicle with a 400 mile range. Once you have that 75 miles of range (battery pack of around 10-20 kWh), is it then better to add on another 40-100 kWh of battery as a "range extender", or to add a combustion engine and fuel tank as the "range extender" to get you to the 400 mile range?