As said, not all secondary objectives are counted towards the progression of secondary objective complition missions.
In Underground for instance, while attacking, only succesfully exploding the generators during the first part seem to count, while repairs on the lower floor generators don’t. On dome on the other hand, repairs seem to count.
Capturing the point in the terminal after it being captured or exploding the generator during the first part while defending don’t count at all.
I haven’t memorized the situation for other maps, but it seems to be very situational.

Did all 4 side obj, 2 main obj and rode 1 elevator.