The Zevo 600 has a 255h kWh drivetrain capable of 342hp but was detuned by 12% to 302hp and 390 lb.ft or torque for durability. This a common practice with EVs depending on their type of use and it's no surprise that GM did it here.
It makes sense, a delivery van doesn't really need that much horsepower, even at 302 hp it's more than enough. Especially when it still has 390 lb-ft of torque.