Recently, I had the opportunity to test Mac-to-Mac iCloud sync; here is the only trouble I encountered:
(1) new note created - appears immediately on second machine;
(2) date (or the range of days) set - sync perfectly;
(3) date changed - still perfect sync;
(4) date removed (by deselecting days in calendar popup) - nothing happens, note on second Mac still has a date set previously.
The issue also affects notes with date removed “automatically”: when I try to manually reorganize already sorted notes, Agenda proposes date removal to avoid inconsistency. Interestingly, on second computer note keeps the date, but goes up or down on the list to match the order on the first machine (screenshot enclosed).