But a 6000 pound truck doesn't get replaced with an EV sedan. Or vice versa. As things move to EV I don't know why the proportion of car body types (whatever you call this) wouldn't stay the same.
Also, cars designed as pure EV's are a lot lighter than EV's built on an ICE chassis.
A Telsa 3 is about 2% heavier than a BMW 3 whereas a Ford Lightning is 20% heavier than the comparable F-150.
Table 2 in the paper lists which cars where compared, and that 24% numbers is an average from comparing models where manufacturers offer EV and ICE variants.
It's the same problem as giant phones. They make them this way in order to fit a bigger battery in.