Well you ask good questions.  But you don't seem to realize that Greece was far from neutral:  it was squarely on the side of the British.  Mind you, I am glad they fought for the Allies, but they paid a heavy price, both during and especially after the war, when I believe they suffered more casualties than suffered by the USA in the entire war.  As for Calvocoressi et al, the text speaks for itself.  I guess one synthesis is as follows:  Greece could have, like I believe Hácha's government in Czechoslovakia in 1939, authorized capitulation to the Germans, and avoided the bloodshed of the Athens occupation and more so the Battle of Crete.  But this is alternative history.  And besides the Greek resistance was a moral boost for the allies, even if you don't believe that (as most neutral historians do not) it delayed much, if at all, German's invasion of Russia.