Your statements apply accurately to low frequency AC chokes and transformers. Things are much more complicated at RF. Take a look at the work that has been done by K9YC, he explains it all. He found that magnet wire is a poor choice for RF chokes. A brief quote from K9YC's Choke Cookbook: "Enameled copper pairs have much greater loss than other paired lines. This is because the magnetic fields produced by currents in very closely spaced pairs used as transmission line cause the current to be concentrated in the side of the conductors closest to each other. This mechanism, which is strongly related to skin effect, is called proximity effect, and is what causes differential current to flow on the inside of the coax shield. Just as skin effect forces current to the skin of the conductor, proximity effect forces it to only one half of the skin! Proximity effect rises rapidly as the center-to-center spacing approaches the conductor diameter, which is the case with enameled wire. As can be seen from the table of measured transmission line data, the enameled pairs have significantly higher loss (and greater dissipation) than other paired cables. It’s also possible for the enamel to be scraped by the ferrite core during winding, shorting to the core at multiple points and significantly degrading choke performance. For both reasons, I no longer recommend chokes with enameled wire."