I believe the intent is to group the grounded conductors of a MWBC when in a gutter, wire way, junction box ect, how ever if you went to article 100 and looked up enclosure it may not apply to switch boxes or 4 squares.
2014 NEC Change
New 200.4(B), Multiple Circuits, requires grouping the common neutral
conductor for multiple circuits with their associated ungrounded conductors
when contained in the same enclosure. New exceptions were also added
to relax this grouping requirement where the grouping is obvious or where
looped conductors or conductors simply pass through the enclosure.
:?
2014 NEC Change
New 200.4(B), Multiple Circuits, requires grouping the common neutral
conductor for multiple circuits with their associated ungrounded conductors
when contained in the same enclosure. New exceptions were also added
to relax this grouping requirement where the grouping is obvious or where
looped conductors or conductors simply pass through the enclosure.
:?