Douglas never accepted or understood the difference between simple flying experience and vital combat experience. He didn't perceive a difference between operational and non operational fighter pilots. Some on this forum suffer the same problem

For example on 31st October 1940 Douglas wrote that the pilot position had undergone a "kaleidoscopic change" and that in the case of Fighter Command "we are actually faced with a surplus." Evill made a more realistic assessment. At the end of July there had been sixty two squadrons and 1,046 operational pilots. At the end of October there were sixty six and a half squadrons and 1,042 operational pilots. Total wastage in those three months was 1,151 pilots, twenty five every two days. Fighter Command, Evill concluded, was "at about the lowest ebb in operational pilots" at which it could function.
This is after the 'stabilisation' system was introduced on 8th September.
All 11 Group squadrons were 'Class A' with a minimum strength of 16 operational pilots. Some 10 and 12 Group squadrons were also designated Class A, but there minimum strength of 16 pilots need not all be operational (a distinction lost on both Douglas and Leigh Mallory). This was because Dowding insisted to Park that they must retain some operational squadrons outside 11 Group to exchange for the most exhausted squadrons in that Group.
Class B squadrons were to retain 6 operational pilots in their quota of 16.
Class C squadrons were to retain only 3 operational pilots and these squadrons themselves were not really operational squadrons.
Fighter Command Head Quarters would inform 10, 12 and 13 Groups daily of the number of pilots required from them for allotment to 11 Group. These men were supposed to be fully trained. Men from OTUs were sent to squadrons outside 11 Group to finish their operational training as 11 Groups commitments left its own squadrons unable to do this.
Richard Saul of 13 Group had previously always sent experienced units south to 11 Group and now he sent his best trained men as part of the stabilisation system. Leigh-Mallory had always retained his better squadrons in 12 Group and now he did the same with individual pilots.
In July and August 1940 squadrons sent to 11 Group from 13 Group were credited with 43 aircraft destroyed for the loss of two pilots. Those from 12 Group with seventeen aircraft destroyed for the loss of thirteen pilots. Even allowing for the inaccuracy of the credits this is hard evidence that Leigh-Mallory was sending less capable and experienced squadrons down to 11 Group and that this practice was being paid for in the lives of young pilots. That is about the most damning indictment of Leigh-Mallory that can be made.
Cheers
Steve