This commentary makes all sorts of sense to me. Especially as someone who, like Rab, was NOT there at the time and has come to the entire body of 1960s jazz retrospectively.
I think the historiography of jazz -- which is in a continuous state of evolution, and apart from the evolution of the music itself -- is an important piece of the puzzle for understanding why some artists are ignored by critics, historians, and other cultural "taste makers."
Think about an artist like Ahmad Jamal. When I first was digging into jazz in the 1980s, authors would go out of their way to denigrate him as a mere "cocktail pianist." In short, his most important attribute was the influence he exerted on (the "far more important" artist) Miles Davis.
But the critical narrative around Jamal has changed dramatically since the 1980s. This is due to all sorts of factors. But, in essence, his body of work hasn't changed but people's perceptions of his body of work have changed.
You could say the same thing about many artists. Their perceived value varies depending on circumstances that have nothing to do with their art itself. It has more to do with the values of the people making judgments about it.