After taking another look the rules in 240.5(B)(2) included conductors 14 and larger. I think the code language in 240.5(B)(2) needs fixing. As I re-read it, you must use fixture wire anytime you are protecting the conductors at the ampacities listed in that section. Some types of fixture wire is available in 12 and 14 AWG, but I think the code needs fixing here. Not sure there is any reason to have the OCPD rating based on the type of insulation on the conductors. The insulation type is the only real difference between other conductors of the same size and fixture wire.If you are using smaller than 14 AWG I agree, it must be fixture wire, my point all along here has been that use of tap conductors is not limited to fixture wire only.