It's a tongue-in-cheek description of how buses and trams work. ie: It's not a new idea, we just tacked "driverless" onto it.
I think the idea is that they could go full speed in sync, then afterwards they could still take you to your doorstep.
The commenter was being sarcastic about trains I think, but while we should be using public transport where possible there is sometimes a need for door-to-door transport so I don't see why we can't explore new ideas that may combine some of the advantages of both for certain use cases
Trams are pretty ok
Tube/metro too.
In high to very high density living contexts, when done right, yes.