TBH, those tests are mostly marketing failures. EV trucks aren't really good at hauling trailers over large distances, as the aerodynamics produce a massive impact on range.

Multiple tests have shown this by showing 50% or more range reduction from pulling lightweight, non-aerodynamic loads.

The marketing failure is that the companies have allowed consumers to incorrectly extrapolate from this to thinking that heavy loads in the bed have the same issue. They actually don't as weight is a minimal impact on range.

Unfortunately, every thread about carrying sheetrock, rocks, mulch, etc shows how misinformed the average consumer has become in this space. It has to be a significant impact on sales, given that in the US these are the only heavy loads carried by >50% of the half ton pickups sold here.