Pg 44 of the nov NECA guide's 314.22 states the 'significance' of the 02' change as...
Installing surface-mounted boxes over existing flush boxes, to make aditions to electrical systems is no longer permitted.
This revision permits surface extensions to be made only from flush-mounted boxes with extension rings.
HUH? What?! 314.22 Exposed Surface Extensions.
Surface extensions from a flush-mounted box shall be made by mounting and mechanically securing an extension ring over the flush box. Equipment grounding and bonding shall be in accordance with Article 250.Exception: A surface extension shall be permitted to be made from the cover of a flush-mounted box where the cover is designed so it is unlikely to fall off or be removed if its securing means becomes loose. The wiring method shall be flexible for a length sufficient to permit removal of the cover and provide access to the box interior, and arranged so that any bonding or grounding continuity is independent of the connection between the box and cover.