This is not the former, this a step in the R&D process that is working toward the latter (and can act as PR in the meantime).

I expect that "supervised by humans in the driver's seat" here means "the car is fully self-driving, but we're still doing development and testing and we don't trust it enough yet". You can test these things on private roads, but eventually you need to get them out into the real world and collect data, figure out where the failure points are, etc.

But for sure they're building a fully-autonomous no-driver-needed car, and it's not ready yet so someone has to be there to take over when it fails.