In essence quite right it seems to me.
There is a book called "617 Squadron" by Tom Bennett in which one chapter is devoted entirely to one Flight Sergeant McLean who had already won the DFM and had mastered the corkscrew technique providing the pilot acted at his command. Tom joined 617 Squadron from 4 Grp at the time Leonard Cheshire was the CO. The CO decided he would put Tom McLean in the crew of a Canadian, Flt.Lt Bill Duffy, the crew being affectionately known as "Duffy's Mob."
The initial action was what Tom called "ready to corkscrew port/starboard" just before the fighter was trying to get into effective minimum range and then use the word "drop" which then required the pilot to haul the throttles back which would cause the aircraft to slow rapidly and suddenly bring the fighter into range and a terrible surprise. At this point the corkscrew would commence under the gunner's commands. Then the pilot would open the throttles again to where they were previously.
They practiced the manouver many times over The Wash with Mustangs who could not get the hang of it at all, and were 'beaten' each time.
The night that went down in history for 617, amongst its many other achievements, was its attack on Metz in March 1944, or it would have been if the weather had been OK, but they were re-called and it was soon after that three Me 110's and one Me109 attacked the Lancaster. After "brilliant" corkscrewing, as Tom McLean called it, he shot down ALL four - with the technique being used to great effect.
Now, it may be that others had not practiced it to the quality of "Duffy's Mob" but it was certainly used most effectively in the space of 35 minutes!
Tom McLean was awarded the DFC for that action and was also promoted to Warrant Officer.
So, it seems by and large, that the corkscrew was VERY effective if performed the way it was in March 1944 by that particular crew.
I am afraid I may not have given the true flavour of such a truly remarkable action, and reflected so well in Tom Bennett's book, so I would recommend you get it if you can. There are other sensational chapters to buzz the mind!
PPP