Hi, George;
I never claimed that they couldn't be used as a firestop/draftstop, only that 334.80 doesn't state whether they're okay or not and shouldn't be taken as blanket approval...only that if they are used as such you need to derate the conductors.
I agree that 300.21 says "Electrical installations in hollow spaces, vertical shafts, and ventilation or air-handling ducts shall be made so that the possible spread of fire or products of combustion will not be substantially increased. Openings around electrical penetrations through fire-resistant-rated walls, partitions, floors, or ceilings shall be firestopped using approved methods to maintain the fire resistance rating"; but as I read it it's still up to the AHJ to rule up or down on what I'm using to close up my penetrations.
As to the suitability for the use I, as always, defer to the Building Code.
