If you're carrying ords, you're attacking something...unless you're weird and fly around waiting for the eggs to hatch.
Attack mode for 4 engined buffs. After all they are carrying ords so they must be attacking something.
If you change it then all fighter sorties that also carry ord will have to remember to select fighter mode. So the guys that fly nothing but fighter mode will whine.
Except the guys that 'really' dont care always fly nothing but fighter mode even when they carry bombs. The only possible reason you could want this changed is if it messes up your score and that means... you care about score. Carry on asking but its been wished before and... denied.