This isn't true for any modern car. Even my 2006 VAG shitbox has a double locking feature, where locking the doors from the outside disables the handles on the interior and the unlock switches.
It's a pretty standard feature here in Europe. In any case, if you've locked the doors from the outside, there should be no reason for the internal handles or unlock switches to be operational.
Ok, so I'm on a longer drive, and a passenger falls asleep, but I need to stop and go to the restroom.
Should I a) force them to wake up and either leave the car or be in charge of the door locks b) leave them asleep with the doors unlocked c) trap them in the car?
Of course, I understand Europe also likes to have keyed both sides deadbolts, so I guess you always need to check if everyone inside the house has a working key before locking the door when you leave too?
I mean, I tell myself not to lock my keys in my car, but it has happened on occasion. Do you think you'd be able to escape your car if locked in? I feel like I may be able to kick my way out or otherwise break a window, but I'm not completely sure of that.