I have had this discussion on here before, but it was about whether or not EMT was included in this requirement, my argument was 300.4(G) ( (F) ) in 2008
states:
Where raceways containing ungrounded conductors 4 AWG or larger enter a cabinet, box enclosure
Which means that the raceway enters the box, it must have a bushing if the conductors are #4 or larger, the only raceway that does enter a box is RMC, and very often can have a sharp burr inside of it when cut, EMT on the other hand does not enter the box, the fitting does, and most EMT fittings have a well rounded lip where the conductors exit the fitting.
But this is only an opinion, so hammer away:grin: