It's not premium priced. It sells so well because it's the cheapest 5kW charger available. Others are AIOs with the same picky input voltage requirements or significantly more expensive.
Remember EG4 is an importer from China, not a manufacturer. So, while they market the charger as being built for those batteries, they're likely made by different companies and someone didn't fully vet the comparably, they missed cable length. Or they expect that many use bus bars and circuit protection and aren't connecting the output directly to the batteries.
Carefully cut the outer insulation and move on with life.