This is complete speculation but my theory is the ones going for interviews are what was left from the first round of intakes.
Example. 2x squads 24 = 48. failure rate say 10% = 5. 48+5= 53 round up to 60 applicants tested.
After 48 recruits taken the left over applicants will go to interviews, plus the testing of the keep fit pool and the ones who have already passed interviews but not proceeded yet.
Purely by statistics the 'keep fit' who received a no thank you letter will have missed out because of numbers available for this year and historical failure rate of the process.
So by the time the new recruitment drive has been given results, at the end of the year, 2 more squads will have been selected from the remaining.
SPECULATION ONLY, im just try to be optimistic for my own situation