[elihu]

Perhaps the version of the upper stage they're launching is not equipped with whatever the relevant control surface hardware (ailerons / grid fins / etc..) is?

[wmf]

It has everything.

[bryanlarsen]

But they're obsolete. S24 uses hydraulic actuators, S27 uses electric actuators.

[mjevans]

Mass distribution consistency is important. They can't just lop them off and change the design ad hock.

[macintux]

Just fyi, “ad hoc”. Latin.