FYI--I've been slowly amassing all Theatre GRO's from the NA. I don't have those that pertain directly to Galipolli (yet). But I do have 100% of Salonika, A good portion of MEF Egypt and a good portion of Italy.
All these theatres instituted a uniform rotation between SD and KD. Galipolli may have been the inspiration.
Attached is MEF Egypt for Jan 1916 and you can see SD/KD change-over occured April to NOV. By 1917 the dates were tweaked abit to go from 15 March to 15 October.
I have not made digital images of Salonika yet, but I believe us of SD was continud a little longer vice Egypt Palestine--My paper copies are buried at the moment.
I suspect Gal. was nowhere near this codified, a bit of a muddle planning wise initially, and the inspiration for this concept.
Hope this is of interest.