This is not a flaw. It is the index being honest about the book’s central tension: two men, unequal in the world’s eyes, made equal only by mathematics.
The index, by giving it one line, mimics the biography’s own restraint. Kanigel knows we want the romantic tragedy—the dying mathematician shipping formulas home. The index refuses to overindex the miracle. It trusts you to find it. Index Of The Man Who Knew Infinity REPACK
And that, perhaps, is the real infinity: not the equations, but the spaces between the page numbers. This is not a flaw