I understood that the delay was to accommodate late promotions to Sqn Ldr so that the full 3 years could be served in order to secure the increased pension, but still leave you with an option. So if promoted at 36, with an original option at 38, PMA would on a case by case basis, extend your option point to 39/17. It was offered to me because of the combination of a) needing me to take up a Sqn Ldr post at that time but b) not needing me after that, being an ME GD(N)! There would be no reason for PMA to make that offer at 44 unless you were offered Wg Cdr aged about 43 I guess.
Err, I delayed my option by a year - as a Flt Lt.
I had a chat with my Desk Officer about the sort of jobs I was after if I was to stay in. None were currently available, so she agreed to delay mt option a year. I rang a year later to ask about the jobs - and the new Desk Officer didn't know what I was talking about... So I put in my option - and left on my 45 birthday...