You would be incorrect on the Volt's technology, but correct on the Bolt being a different vehicle. I remember the Bolt now. It's that same piece of crap I'm talking about like the Leaf and Prius. It's a deathtrap that sacrificed safety, power and stability in order to lower price (because stupid consumers fall in love with the idea of "electric" vehicle without looking at what they are actually getting.) The Volt got 62 mpg because it converted it's gasoline into electricity even though it had so many more power requirements than a vehicle like a Bolt, Leaf or Prius. The Volt is far superior than any of them, which made it the all-time top-selling U.S. plug-in electric car and the world's all-time best-selling hybrid electric car.
From Wikipedia (so you have a reference).
The Volt operates as a pure battery electric vehicle until its battery capacity drops to a predetermined threshold from full charge. From there, its internal combustion engine powers an electric generator to extend the vehicle's range as needed. When the engine is running it may be periodically mechanically linked (by a clutch) to a planetary gear set, and hence the output drive axle, to improve energy efficiency. The Volt's regenerative braking also contributes to the on-board electricity generation. Under the United States Environmental Protection Agency (EPA) cycle, the 2013/15 model year Volt all-electric range is 38 mi (61 km), with a combined electric mode/gasoline-only rating of 62 mpg‑US (3.8 L/100 km; 74 mpg‑imp) equivalent (MPG-equivalent), with a range of 420 miles. Not bad for 7 gallons of gas. This is the technology that people want, but at a lower price. That's not possible. People are going to have to pay more or else by these cheap and crappy cars like the Leaf, Bolt and Prius.
Chevy had to come up with something cheap, I guess, when Obama (since rescinded by Trump I think) required a certain percentage of all vehicles manufactured to be electric.