Isn't this wrong?

The article states that cars are unable to use chargers that are rated over 50kW. Surely cars can use the chargers, but not at rates over 50kW.

The reason is obvious. PHEVs have small batteries and charge rates are dependent on the size of the battery. If you don't want to damage the battery you're going to be limited to below 2C (twice the capacity per hour). With anything less than 25kWh in size, you won't reach 50kW. PHEVs have batteries in the 10-20kWh range.