I mean, that's not the methodology of the attack... if the methodology I described were used the attack would not be possible. You are saying it is not possible to implement this mechanism on BLE without affecting the user's experience and, if someone had tried for this key, they wasted their time as they didn't understand how BLE worked. While I am honestly skeptical of that--as I would expect I could use a different packet with a new local timestamp for each of these "reconnections"--I don't know much about BLE, and so am willing to take your word for it; but, as we clearly aren't going to want to synchronize the clock between the car and a silly little key fob so accurately as to allow us to deal with the time difference of the speed of light moving across a mere parking lot, the conclusion to me is that we can not use BLE (which I would think is overkill for a key anyway) and instead must use a more trivial radio scheme.