Earlier quoted context omitted.
Regardless of the definition, I can't buy and own such a "driverless car" because I don't operate a supervision center with people available to "assist" the car. Whatever "assist" means. Nor can any company that's not large enough to operate the infrastructure. I'm sure at least some of the hype is in regards to people owning such "driverless" cars. It's driverless by definition because it does not have a driver, but…
Since the assist doesn't require real time response (e.g., the failure mode is the car not moving, not you dying unlike a tesla) it seems like a non taxi version could simply set you up as the assist monitor. If you fall asleep or don't respond it's fine, you're just stuck. I don't think Google plans to do this for a variety of reasons, but I don't think there's fundamentally any reason they couldn't.
"Just" being stuck on a highway doesn't sound too safe. If you have multiple supervisors watching the fleet it's less of a problem than when it's one fallible supervisor.