I suspect the ECU is giving you a lower range because of the colder ambient temps. Put simply, EV batteries and motors are much less efficient when the mercury drops below double-digit Celsius.

My BMW 225xe's indicated EV range in summer was 20 miles; in November that would drop to 14 (15 if I was lucky). The difference in EV performance when the ambient temps were higher than 10 or 11C was quite noticeable too. Much nipper when it was warm outside.

In addition, autumn/winter use will use the heating and lights more.

Range calculation has always taken previous driving style into account, whether petrol, diesel or electric - a default value is used when new but this gradually adapts to your own style and driving conditions - it's a similar technique used with adaptive transmissions.