Which one and according to which regulations will this be installed and tested for functioning properly / safely? High voltage DC contactors are expensive and bulky so car manufacturers are not going to install these if they don't have to.
You really need to look at some teardown video's and talk to people designing such cars ... instead of spouting FUD ...
There IS a HV contactor in the batteyr pack. It will be shot open under certain conditions. It is an explosive charge to guarantee the thing opening and potential arcs/sticky contacts being extinguished and remediated. It has its own redundant backup , even if the local 12 volt system fails and there is a catastrophic short on the high voltage bus and the pack is somehow damaged : the contactors chemical charge WILL still fire fromt he embedded supercap in the contactor.
Just like you have a mechanical clutch in a mechanical engine you have an 'enable' pin to the inverter driving the propulsion motor. set the enable to low ( by clicking the stalk on the steering wheel in neutral ) and the motor goes in coast. This is a hard-wired , not software controlled gating on the power mosfets. Even in case of a cut control wire the system ios designed to fail-safe. ( meaning motor switched to coast ).
I have the impression that you think that these newfangled electric cars are designed by a bunch of muppets ...