Keeping boilers hot or heating them up just before they’re needed uses less fuel than continuously making electricity. Lets not make false arguments to defend our positions. They can easily be shot down.
It’s true that there is less fossil fuel used, but heating up boilers takes many hours. Germany is moving back to coal after tilting at windmills and subsidizing solar as much as 50 cents a kWh wholesale. Anything more than a few percent of penetration with intermittent sources requires hot standby power. That means the same amount of fossil fuel use. Putting in a few percent solar and wind (other than Texas which is a special case) is not going to reduce fossil fuel use by more than a trivial amount.