You are thinking correctly. The base load generators are slowly needed less fuel till mid of the night. What this plant is doing is providing peak energy at peak energy times, reducing ( not eliminating ) the need to bring on the gas turbine plants to cover the low supply and high demand moments.
it's small steps like this that will over a 30 to 60 year period of time reduce our consumption of fuel.
next small steps that I would like to see, that all roofs in the lower part of the USA be required to have at lease 20 percent of the sun facing portion covered with solar power panels within 45 years ( life cycle of a roof is about 30 ). I use 45 years since we could provide real estate property tax incentives to those developers and home owners starting now, and in 45 years make it mandatory.
I keep thinking it's needs to be done in small steps, the early adopters get more benefits due to the extra risk they are taking ( wind might lift the roof due to the panels, fire risk because of a bad install ... ). and as demand increases we might benefit with smart electrical grids.