Moaning about missing the qualifying date is a bit like saying "I joined the Army the day after VJ Day and didnt qualify for the WW2 medals". Some you win, some you lose.
The reserves already have a long service medal (VRSM) which can allow some regular service (I believe) to count towards reserve service in some cases.
Ultimately there are bound to be a small number of people who feel they've missed out, but overall its not a bad solution going forward.