[majoe]

Some thoughts on why I think this is wrong:

If no one needs it during the day, they can't sell it. That's not how markets work. Energy that is generated, needs to be consumed or else the grid breaks down. These two facts together mean, that the energy they sell is needed and used. Albeit they could generate and sell even more energy, if the energy could be stored or if the load could be shaped accordingly. The latter is a great way to lower energy costs.

Energy consumption during the night is low. So low, that night time electricity prices, which are lower than the daytime prices, are still a thing.

Heat pumps are an opportunity for load shaping. Buildings can be heated, when electricity is abundant and heated a few degree over the target temperature, if needed. The heat is stored inside the building and needs less heating during the night. That works quite well, especially here in Europe were buildings generally have good insulation and are made of brick, which can store a lot of heat.