There is hardware that could potentially be used for the car to drive itself. It might not be sufficient for safe unattended operation, but there is hardware that can steer the car and make it move.
They have a design for a system that could drive the car unattended. It could be a piece of paper that says "Requirements: car must drive itself" with a couple boxes and arrows, or it could be more elaborate.
They might deliver software that can be left unattended. Or they may not, who knows.
They can deliver updates over the air.
Is that what people expect? Probably not. Can you currently sit in a Tesla and go from A to B safely without paying attention to the car? No. Will they ever be able to deliver the experience that the average person expects after reading the second paragraph? Maybe, maybe not. Will it be reasonably safe to leave it to drive unattended? Who knows. Would the average person who paid for "full self driving" feel deceived if they never delivered that experience? Probably.
It's definitely been crafted to describe something that might potentially be delivered someday, yet leaving enough wiggle room to be able to say "we never said it could be left unattended and never promised we'd ever deliver something that could be" in court.