Isn't what you are describing actually L4 autonomy? At L3 the human still needs to be attentive and ready to intervene at very short notice - so you definitely

Isn't what you are describing actually L4 autonomy? At L3 the human still needs to be attentive and ready to intervene at very short notice - so you definitely cannot eat a sandwich or text while in the driver seat. L4 autonomy is where the vehicle is fail-safe. It cannot handle all conditions, but is able to recognize conditions it cannot handle and hand control back to the driver. Importantly if the driver is not responsive to takeover the vehicle can put itself into a safe state (mostly just means pulling over in a safe place). L4 is the minimum at which you can be fully distracted from driving. I don't think Tesla has a viable path to L4 using its current hardware...