All of this is true but you need to look at the wider piece. If a SNCO does time served then this is a good argument - quite expensive if taken as a single point.
If you add in the training burden for Pilot Officers (IOT and flying trg) who do only 6 or 16 then it adds up to a saving. A steady wage is easier to manage on a 3 year basis (gov way!!) but a roller coaster training pipeline is not easy to manage - remember the MFTS piece in this - a Civilian company with budgets fixed well in advance of the moment - might be a factor.
NCA Commissioning is great in branch and a full career path is a must but it gets very tight at the top, a better way might be to allow them (the great) to move within a band associated e.g. not on the ground (not that ATC/ground trades can’t apply – I know they are out there and quite highly qualified at that)
L28 would be used as a retention incentive, as PAS is at the moment, but I think it is to keep Army SNCO AH pilots in the main; not a bad thing if it helps others but must be bought into the mix of this thread.