I would agree, and there is often a world of difference between what shows up on a graph and what's audible. Quad are different to almost all audio companies today in properly researching what was actually audible, then ensuring they built to satisfy that spec with a little headroom.
There weren't an audiophile company in the sense we understand the term today, and Walker views toward the audiophiles of his day are well documented. He couldn't understand the fixation on minutia being assessed without controls or references and he was right IMO.
The proof of the pudding is to connect a standard 405 to a pair of 63s and see if you get 'muzak'. In 2013 I've had three visitors poping over specifically to hear ESLs. Two have bought 63s (within weeks) and one intends to. Ok, its not a standard 405-2 but it only has slightly larger PSU caps and a quieter input. The one memorable comment from all is that the 63s don't sound as they expected, specifically they do have low bass, do go loud, aren't soft and do have dynamics.
Less talk and more demonstration is always the best policy.
Yes, that's the only way, with some controls in place.
You can make an analogue switching IC or ancient jfet op amp look crap or wonderful, depending how they are used. Distortion from both is very sensitive to load impedance. The 44 and 34 is designed with this in mind and both types of device are used optimally.
Both pre amps use many such devices in series yet you'll typically see 0.008% THD from these inadequate devices. The 66 pre amp continued to use them into the 90s, precisely because they work well enough. I've pulled and replaced every switch and op amp on a 34 with technically better modern versions, with appropriate attention to local decoupling to ensure they all work correctly. Doesn't improve the sound. The phono stage can benefit from something al little better than was available in 1980 so that's worth fitting but don't go mad - OPA134 is ample.