I have just noticed that the date picker on iOS behaves differently than on MacOS. For example pick a defer date on iOS then pick a due date, the previously selected defer date is carried over to the due date picker. This does not happen on MacOS.
For example defer something two weeks, and if it is due one day later you just have to add one day in the date picker.
It would be nice I think if this was included in the mac version as setting a due date based on the defer date seems a logical action?