Locking the car doesn't seem to be dependent on distance. We can be loitering by the car for a few seconds (about the time that it takes to get the charge plug and walk to the back of the car) and the car will have locked. Sometimes scares the life out of you if you are bending down beside the car.
Being in bluetooth range doesn't mean that the car can be unlocked at the car. You can check if car is in bluetooth range as some of the controls in the app are active, which allows you to unlock the car manually from the app. To be able to open the car in a keyless manner, ie by pressing the handles, you need to be much closer - I don't have a distance, but its quite close, to the point that for some people having a phone in their back pocket is enough for the car not to open.
When the phone comes within keyless range, the car does not react or wake so the car being ready to open is totally stealth. You need to physically open the car for it to wake, and sometimes even that takes time to trigger.
TBH, the only real way to know is to physically try different situations and phone/car placement. I did this on several occasions and confirmed that its not even remotely a problem for us.
