I just learned that the Canadians had majors as company commanders and a captain as the EO. What about the British Army and Australians?
Appears to have been the same in the British Army, if this is anything to go by. And probably the Australians too https://www.battleorder.org/uk-rifle-co-1944
IRRC the British Army re-graded company commanders as majors in the 1920s. They had been either a major or captain in 1914, possibly a hang over from the conversion of ten companies to four in the 1900s. Artillery battery commanders had been majors and this may have been a levelling up of the ranks of sub unit commanders. The British had rank inflation over other armies which typically had captains commanding companies and batteries. Still paid less than a US Captain or sergeant. . In wartime many of the company commanders would be substantive (= real rank) lieutenants acting (temporary rank) captain or major and substantive captain acting as lieutenant colonels and even brigadier generals (e.g. Bernard Freyburg (WW1) and Michael Carver and John Durnford Slater WW2 )
Is that possibly why most PoW commandants in this country seem to have been Captains or Majors, in addition to having been prisoners themselves in the Great War?