They should all get it but only back as far as 2006, the day we BOUGHT YOU.
On that day the ASL should have been one list.
So a person that has a KA DOJ of 1990 would only get 2006 for staff travel etc.
CX have never explained to any new CX employee that joined since 2006 that this would be the case. ( they come behind all KA that were employed at the purchase date )
It's happened to me in another life and my Airline also didn't explain. After a year I lost 250+ numbers to the other Airline we bought simply because I joined AFTER the purchase date.
So 2 choices for you I think:-
1/ Pri 25 with a seniority DOJ no earlier than 2006
2/ Pri 26 with your original DOJ in KA.
Make your choice.