If I had any kind of access to my car's filesystem (even read-only), I would spend waaaaaaay too much time poring through various configuration files, looking for clues about the car's behavior.
The JSON file that defines how voice input is interpreted and mapped to a command is a great example. From that one file, we know which actions can be initiated from the voice recognition system, and what specific phrase(s) we can speak to trigger each command. To my knowledge, this information is not documented anywhere else, at least not to this degree of nerdy detail.
some feel the need to hack into the car and detail it's deepest processes. that is great and there are a few guys who are really top notch at working the code, they are so good at it that tesla has reached out to them for their input, but be aware that this sort of digging in deep into the car is not for the casual hacker, you could become the owner of a very expensive brick
I don't think Tesla is giving any hints to "hackers". This is a very normal thing that happens with any great product, Tesla has amazing engineers but this kind of tinkering might help patch up some holes.