The interesting part here is that is about whole games, entire days if elevated performance, not just a few very lucky shots every game.
This means it's a state of mind / brain / CNS that can be entered and sustained for many hours. An ability to do that on demand, or at least predictably, would be of a huge practical interest. The ability to avoid the opposite, low-performance state, equally so.
My experience is that it is not possible enter such a flow state on demand. The state is beyond "my" control. There appears to be "a part" (not necessarily a physical part) of us that we think is "me" that wants to control, i.e. micromanage, and "on demand" means that this part would decide, i.e. able to control the flow state. However, the state seems to happen when this part lets go of the need to control things, and seems to disappear when this part tries to control things. The whole discussion is too long for here, but I recommend book Inner Game of Tennis for details.
This means it's a state of mind / brain / CNS that can be entered and sustained for many hours. An ability to do that on demand, or at least predictably, would be of a huge practical interest. The ability to avoid the opposite, low-performance state, equally so.