This is not how curtailment works.

Curtailment is when an energy company has successfully bid on delivering electricity for the next block of time (an hour, for example) but it can’t provide that agreed amount of power because it would overload the grid. There are various reasons why that would happen: faults and unexpected lack of demand, for example. In that case the company is paid for the energy it was contracted to deliver, only for that period of time, even though it did not provide power.

It is wrong to say that overproducers HAVE to be paid. They don’t. They only have to be paid if there was an agreement to buy that power but for whatever reason the grid can’t take it. Normally if there is a generation surplus, the cheapest companies will win the bid to provide power and the others will simply not be paid.

The utility SHOULD ensure there is enough power for the worst case. Which is why they will sometimes pay someone to not generate power.