Note how the code reads. It does _not_ require re-identification of the white conductor. Instead it _permits_ the white conductor in a cable assembly to be used as an ungrounded conductor in three possible uses. a) If it is re-identified. b) if it is the supply to a switch loop _and_ it is re-identified. c) If it is part of a flexible cord used to supply equipment. Note that in situation c) re-identification is _not_ required, and it is assumed that an electrician will understand how the conductors in the supply cord are being used.
In previous versions of the code, situation b) did not require re-identification, and it was assumed that an electrician would know how a switch loop operated and that re-identification was needless redundancy. It was clear that the electrician had the _option_ of re-identifying the conductors if they wished to use the white conductor as something other than the supply to the switch loop.
-Jon
