I actually pinged some professional code slingers so that you could get a second or third opinion from known authorities on the matter (i.e. "don't take my word for it").
Physical possession of the hardware by the best of state-supported (i.e. unlimited funds) hackers makes security very...mmm...problematic.
For example, the code in question must be decrypted prior to each instruction being executed by the CPU (otherwise the CPU doesn't know what to do). Well, with physical possession, a hacker can put physical electrodes onto the CPU inputs. This enables the hacker to see the instruction being executed.
Do that long enough and in many cases you'll have the whole software program.
And this is just one example of "possession hacking."