Bit of speculation here ...
Might it be that it's because Rose is such a thorn (pun intended) - a prick, even - that this is why some have thrown in the towel?
After all he will have done at least four "encouraging" visit to the congregations in his circuit and now will be on his fifth. If you are a doubter or a bit wobbly you might think the first visit could be down to him having a bad week; but when that gets repeated time after time it can be very wearisome.
Talking personally it was one overbearing CO that A) almost made me resign once as an elder and B) another one that made me actually resign about five years later. It was a kindly more reasonable CO in between that made me "hang on" longer than I should have.
Lets hope Rose works his "magic" in another circuit when they get swapped in September because as sure as grass is green I know Vigo and Gillies and Co. at Bethel UK won't have the common sense or humility to remove this idiot!