The news from HMT is that everyone serving on 31 March 2012 and forced onto AFPS15 will be transferred back to whatever scheme they were on at the time. As expected, everyone serving on 1 Apr 2022 will be transferred to the new scheme regardless of age. For the avoidance of confusion that means you will have the choice of legacy or reformed scheme benefits, so you can take whichever option is most advantageous to you.
At the point you decide to take pension benefits, you will have the option of either taking those benefits per your previous scheme or electing for a reversion to AFPS15 wef 1 Apr 15 and being treated accordingly. There should be more detailed information coming from MOD and FPS, as there will have to be some form of adjustment for all those who have had tax bills over the last few years (Scheme Pays etc.) Not sure what they will do about people who paid the bill up front, presumably the remedy arrangements will have to take all that into account.
I think MOD will have a lot of work to do on the details and DBS will no doubt be prioritising those closest to retirement. There will clearly be some retrospective work to provide the same choice for those who retired on the reformed scheme (AFPS15). There will still be tax bills for some...