Government logic of vehicle weights definition ..
"Vehicle weights explained
Vehicle categories on driving licences can depend on the weight of the vehicle - the different terms you might see are explained below.
Unladen weight
The unladen weight of any vehicle is the weight of the vehicle when it’s not carrying any passengers, goods or other items.
It includes the body and all parts normally used with the vehicle or trailer when it’s used on a road.
It doesn’t include the weight of:
fuel
batteries in an electric vehicle - unless it’s a mobility scooter or powered wheelchair"
https://www.gov.uk/vehicle-weights-explained
Just an example on how confusing it is to compare vehicle weights, manufacturers generally only quote the vehicle base weight, that is the weight of the base model without options fitted.