In the beginning of Dune 2021, Chani tells us:
At nightfall, the spice harvesters land. The outsiders race against time to avoid the heat of the day.
Later after having taken over management of Arrakis from House Harkonnen, Duke Leto Atreides and son Paul observe a spice harvester in operation. It's broad daylight.
Despite the change of management, it would have presumably been the same people, or mostly the same, doing the actual harvesting. And their standard operating procedures would likely not have changed. So why were they not also harvesting during the nighttime to avoid the heat of day?