This answer extends on candied_orange's answer. (Permission is given to combine the answers and delete this stub.)
The ReadExistingPlan method does not use the entire ChosenEstimates field. Rather, it only uses its StartDate and EndDate properties. Code clarity would improve if the caller passes in the right amount of information into ReadExistingPlan.
I could supply ChosenEstimates to ReadExistingPlan() as a parameter, but the Clean Code examples almost never do this.
Actually Clean Code does exactly this on page 303:
G31: Hidden Temporal Couplings
Temporal couplings are often necessary, but you should not hide the coupling. >Structure the
arguments of your functions such that the order in which ...