Good lord can we please move away from the common misnomer of kW, MW, GW, and TW when we mean kWh, MWh, GWh, and TWh? It makes me angrier than it should, but aside from BTUs (heating/cooling) it's the only one I'm aware of that is so stubborn.
As far as I read the article they are really talking about 100 MW maximum power output; they mention that the Australian version can supply that 100 MW for a bit more than an hour (so store a bit more than 100MWh), so they seem to be aware of the distinction but apparently don’t know (?) the energy storage capacity of the planned battery installation.