I thought I’d take a look at this database (EV Database) you refer to. In reality it calculates the miles per kWh by dividing the battery range of the car by the battery size and theoretically uses an alogrithm based on temperature e.g mild been 23c with ac off (how many weeks do we get 23c in the UK).
I’m by no means having a pop at you but really its nothing someone with an ounce of mathamatical knowlrdge can’t do at home at their own computer desk. Real world driving I can’ see it being highly accurate in the real world with the majority of EV’s, unless maybe your tootling to the shops and back. Put it this way I have my reservations about such a site but hey I could be wrong..