Yes. And if you remember I highlighted the word if (IF you can handle the volume).
You've cheered me up today Chris by this post I often agonise over whether I do enough training, then when my conscience tells me to push it's limits I end up running worse, just as you're saying. I believe in Lydiard's principles but as you say he assumed everyone had the same kind of physical constitution (the body's ability to cope with training) as his best charges did. Don't we all meet people like that who criticise others for not training as hard as they do/did, and they are usually well meaning, they just don't understand.
I've arrived at what seems an optimum amount of training that I can do consistently without breaking down, which is about 9-10 hours running per week (incl cycling equiv of 2:1) which equates to maybe 80-90 miles. I need recovery weeks even from this, which is good training, but a far cry from what some runners can handle. Or can they? I don't know, lots say they can. And then again a lot of good runners claim to do half that!