Frankly, I don't think it should open unless the phone is right next to the driver's door. Possibly also the passenger's door. The leeway as it stands is too far. Nobody is going to be opening a door unless you're stood next to it, unless you have freakishly long arms.
here's the reason (that I would use) - it takes some time for ble to actually work. channel scanning, exchanges between ble implementations, signals going up and down normally (lots of nearby 2.4ghz rf), sleep cycles in your phone, lots of areas where you need extra timeouts/retries for things like this to work.
I'd like it to 'start working' (start the protocol state machine) as I get near, then as I get *really* near, be at the end of the state machine, and really 'know' I'm there. I've had to wait longer than I should when I walk up and try to unlock.
now, imagine you are in a bad area and you really REALLY want to get the heck out of dodge, now. you don't want to mess around with a silly phone and ble. I DON'T! and so, speeding up the 'ok, I trust you, I know you, you can come inside' - it has to be fast. and detecting me as I come near lets lots of sluggish or latent systems get back up and working so that the unlock can happen at least a little before I'm really there.
I do see this as a safety issue. I could grade the vendor on how reliable and fast it unlocks. its really important that this gets to be as reliable as fobs (and fobs have been worked-out and pretty reliable for decades, now; and very low power, too. I've gotton 10 years on a fob battery for my old VW gas car).
[rant] ble and bluetooth is a mess, though. and so many versions, not to mention 'apple being apple' and not being standard enough to make it easier on vendors; and you *must* support apple, no one can be android-only [/rant]