Its meaningless to compare Tengah to a car heavy matured estate with over crowding stations. I am sure its not HDB or LTA intend to develop Tengah MRT stations to be as crowded as Bishan or AMK.
Yes, I still have my reservation of AV technology being deploy in a non controlled environment such as HDB estate. Even LTA says they envisioned that robot buses to run scheduled services during off-peak periods to complement human-driven ones, while driverless shuttles can be summoned on demand by commuters.
The other consideration for AV is operating cost. Will it cost as much as bus or will it cost similar to taxi. If AV need a dedicated track, it will still take up land space. However the good thing about elevated track is that below the track it can be turn into PCN.
And yes, seeing is believing. So until AV technology is tried and tested in real HDB environment, AV technology will still be a complimentary transport system.