Hmm, let me explain the German army way as I learnt it.

An anglophone scholar (forgot who - either Gudmundsson or v.Creveld) once wrote about it that for Germans (in WW2), battle was the source of discipline itself. He came close.


The German keyword here is Gefechtsdisziplin - combat discipline.
It's the compound of obedience with thinking and comradeship.
A (small9 unit cannot withstand the stress of battle without discipline, thus discipline needs to become natural for army soldiers. It needs to be trained with discipline in little everyday affairs, but the superiors should always remember that it's combat, not the everyday affair that warrants this effort!

This is of utmost importance, for exaggerations that do not pursue the goal of robustness under combat stress will stifle the "thinking" part that's of great importance for actual performance in battle (and for developing leaders).


As a consequence, it's quite unimportant whether all soldiers wear the sleeves up, down or whether they mix it. They may march in lock-step or not.
All that counts is that superiors used enough discipline standards to instil and maintain discipline. Discipline is a skill that need training and maintenance, it is not a performance.