Getting back to the authors question, the Hall has no criteria really. That is, no written one. Its subjective and bias in many cases. Some days all you need is a title and at other times you need more or you don't need one at all.

Why is Kid Azteca not in there?

or,

Harry Jeffra
Tippy Larkin
Esteban Dejesus
Bert Lytell
Jack Chase
Jackie Patterson
Willie Joyce
Rafael Herrera
Ernesto Marcel
Cocoa Kid
Jeff Clark
Lou Salica
Benny Briscoe?