That paper is biased to their point of view. The part about overdamping produces less bass is manipulative as damping keeps the bass tight and accurate, underdamping results in what many call flabby bass. There is nothing bad about an amp having a very low output impedance. A current mode amp can have distortion and nonliearities, it is not magically cleaner than another design, that is up to the individual design. The part about tubes, SS amps and transistor radios is another weak attempt at manipuling the reader's opinion. Some of that paper is interesting.
Well, it's not my business to defend them but they never say that current drive is the only good solution, only that it's a way of doing things that has certain advantages (and to be sure, disadvantages too) that's rarely used nowadays. And there's little arguing that Nelson Pass knows how to build an amplifier. Specifically for the F1(-J) there are a couple of guys who use it to drive their HE-6 and I sure didn't hear any complaints from that side so far, never mind the impedance/damping mismatch.