Large mining machinery (Haulpaks) are the same - electric with a diesel power plant.
I don't believe the wheel weight is a big issue in these cases - particularly for the AC systems, which are somewhat simpler and more robust (in terms of the wheel motor, the actual control system is much more complex).
The reason they use an electric system for Haulpaks is varied - but basically it's due to the fact that a mechanical drive system is almost infeasible at that size/load/torque. An electric transmission system is easier to control and more robust.
Also, electric lets you control the torque much better, particularly in the AC case where they can adjust phase/freq/etc to keep it controlled.
This is how I hope they'll build gas-electric or diesel-electric hybrids in the future.
The article misses the "elephant in the room" point that the electric motors are the easy part. They always have been. It doesn't much matter if you cram the electric motor into the wheel or under the hood. Getting a power supply with enough power density and a short enough charge cycle that its actually feasible for daily use is the silver pearl.