It runs along the following lines:
The introduction of DE will not affect the number of punters turning up at their AFCO to join the RNR - the pre and post DE publicity is much the same.
Pre DE: Of that group of punters, some will want to be officers. They join as ratings, spend a couple of years learning their trade as ratings, and go on to AIB. Some of them will pass AIB because of their time as ratings, some of them would have passed AIB anyway. Some will change their minds and either leave or stay on the lower deck.
Post DE: All those punters that want to be officers will go straight to AIB. Those that would have passed due to time spent on lower deck will fail, reducing the number of officers had DE not been introduced. Some of the extra ones we send, those who would have never gone to AIB had they spent time on the lower deck, will pass, but I believe that the kind of recruit who would change their mind or leave if they couldn't get an AIB straight away do not make useful officers, and will leave anyway or become one of those ineffectual officers you see hanging around at the back.
In summary, my hypothesis is that the removal of time on the lower deck will reduce the quality of officer candidates being sent, causing some who would have passed to now fail, and the extra officer candidates we now send to AIB who never would have made it that far pre-DE make poor officers who do not counterbalance the loss.
It is, of course, early days, and tracking the numbers will prove very difficult.
Note: Of my most recent batch of NE ratings, at least three want to be officers, so maybe the AFCOs are not offering DE to all and sundry anyway.
Note: If you're a DE candidate, and you think my statements above mean 'DE officers are all rubbish'; I suggest you practice your English comprehension before your AIB.