Politics combined with a technological package, in other words.As reviewer of the Ongaku (and designer of the 92d B efficient Ariel) I was drawn into the SE-DHT debate as well - but I never bought the religious angle.I auditioned many SE-DHT amplifiers after that, but in all honesty, none came up to the mark set by the Ongaku, although some came pretty close.
By the mid-Nineties, SE-DHT almost became a religious cult, diverging rapidly away from the mainstream universe of hyper-expensive, super-power amps, low-efficiency speakers, with the whole industry driven by reviews in the Big Two magazines.
(Tests in Vacuum Tube Valley magazine shows DHTs have about one-half to one-third the distortion of triode-connected pentodes, not a small difference.) The reason is clear when you look at the composite curves of Class A PP triodes: the grid-lines are essentially straight and parallel, so when the load-line opens into an ellipse (becomes reactive) there is no change in distortion.
BY contrast, all other other circuits and devices ...
On a statistical basis, the greatest percentage of the time is in the 1-watt or lower region, at least if the speaker has any kind of reasonable efficiency. if you want linearity at low and high levels, near-total immunity from reactive loads, only PP triodes operating in very deep Class A can deliver straight and nearly parallel grid lines.
The very deep Class A operating point keeps the circuit well away from the undesirable Class AB region; this is only entered when the load becomes a near-short, one that would current-limit and clip a SE amplifier.