Of course. Though with increasing deployment of intermittent sources like wind and solar, occasionally the wholesale price can drop lower than the marginal cost of the nuclear plant (or even negative, if said power sources receive production subsidies regardless of the wholesale price), in which case it makes sense to throttle down.

Future grids with more intermittent renewables will have increasingly volatile prices, but not necessarily lower on average. So generators that can produce during high price periods (e.g. if wind and solar aren't producing much) can make a lot of money then, compensating for less income during low price periods.

I'd be willing to bet there are some significant thermal efficiency losses at 100% that would push you down closer to (made up number incoming) 80% at idle

Gas turbines are the ones that ramp the fastest and are used to handle dynamic peaky loads. Nuclear/coal are generally used as the baseline power because they're more efficient.