Obviously, it's better to do this with partial battery charge rather than a depleted battery, but even with the ICE cycling on and off, as someone else stated, the fans will take care of it. I'm guessing the Buick LeSabre had a much bigger engine in 1987, and if the car was old, maybe the radiator full of gunk and wasn't operating at 100% efficiency. Your G2 volt is so new, there shouldn't be any issues.
On really hot days when I'm well within EV range, I'll leave volt running in the grocery store parking lot so the cabin is nice and cool when I return. Nobody know's it's even running, unlike the empty crew cab dually diesel clanging away parked next to me as that coal roller also wants to return to a cool cabin. The only giveaway is the triple honk as I'm walking away from the car. Only a volt and ELR owner would know what I was up to. Most other people would just think I turned on the car alarm or something.