Gilmour book it´s not Lydiard that wrote it. It´s a Gilmour interpretation of "his own idea" of the Lydiard method.
But i don´t want to be fix on that aspect.
I can comment on the kind of Ron Clarke training that is presented.
As far as i know during that Ron was a runner Lydiard and him they meet and talk only once. Then this is picked from original Ron Clake training and edit on the book as Lydiard training example.
However i got somethig more to say about it. If this is Ron Clarke training that you present as Lydiard typecal, i prefer othere from te same period, like Michel Jazy, Kip Keino or Bob Schul.
From the modern ones i prefer many more to this one that you preseent.
One more point. Most of the times that one Lydiard accepts HIBRID Lydiard as one Lydiard training variant, here comes Deek the coach of Castella. I prefer Carlos Lopes training to Bob Castella one from the sam period, it´s much more rational than the Castella one. From the same period of Castella i prefer what i can name the japanese training from te 80s than Castella one.
If i think in alternatives to the Typical/classic Lydiard, there are many more better training ouit of te Lydiard method than the influenced by Lydiard. I could justify, but this is out of the main subject.
About what is the commercial and business reason to keep on Lydiard, you may ask it the Lydiard ones, don´t ask me, i´m not the right man to answer you how is done and wehat the profit.
If you really want to know why don´t you ask to mr. Keshall, or mr. MacMillan or a few the Lydiardists the Lydiard Foundation. If they want, they will answer to your question better than i can do. I just comment about factual motivations and acts.
Of course they got the right to do what they do, but i also can comment about what are facts. It´s was done, is done, i can comment on facts.