Simple answer = both buses == off, easy todo.

Whats the current vecors in General, the HS can is the most important and they  hide it pretty well except in haldex cars.

It''s always been the case man, access to h bus and diag protocols you can take over a car.

Some brands diag overrides physical control too, there's IP based CAN routers I see too lol.

I thought about this from a theft point of view and take the ecu with you lol.

You can also overload the bus = bus off stalling car, etc.  From the many lines of ASM invalid inpus are formally handed in Bosch like cmpb r3 0xff.

UDS supports encrypted comms too.  That's the way to defeat it, and other way and I can only imagine that it anti tuner subterfuge.  Look at what Volvo's doing with Polestar e.g., they've beem using CAN since 98.