In my opinion, you are correct (as is Bob).
I, like Bob, think the "main power feeder" must originate at the service equipment and end at a lighting and appliance panel. If you had a 200 amp panel (outside service equipment), it would be legal to feed an indoor panel with 4/0 AL, but it would be a violation to leave the interior panel and feed another panel with 2 AWG (unless the terminals were rated 75 degrees and you use the round-up rule). Once you have a feeder that originates outside of the service equipment, you are in the land of 310.16, not 310.15(B)(6).
