Not a bad idea actually. Some military storage facilities I've been to are absolutely filthy with dust and mopping off the tops of the lockers is a good call.
We had the Brigade CO coming through our COF annex so we needed to mop the top of the lockers because the were dusty as all get out. He never did come through but at least the tops were no longer caked in dust. Wasn't used as a punishment, being in a MI Co we had much more inventive ones.
He's probably in training, or an FNG.
Still an assignment for a fuck up or FNG though.