Okay, if you assume non-renewable generation that cannot be curtailed, then you are right of course. And your second point is also valid, a small flat rate inf

Okay, if you assume non-renewable generation that cannot be curtailed, then you are right of course. And your second point is also valid, a small flat rate infeed may be easier to bill for the broker than per-minute pricing with curtailment. But this will only be the case if prices aren't negative for too long.