The Feynman technique — explaining a concept in simple language as if teaching it to someone unfamiliar — is a diagnostic tool for genuine understanding: the points where explanation falters are precisely the points where understanding is shallow or absent. Feynman was intuiting what cognitive science would later confirm: that generative retrieval, elaborative interrogation, and the demand for explanatory depth produce far more durable learning than passive re-reading. The Sutras' tradition of the student restating the teaching to the teacher before receiving correction serves the same function.
Each step builds on the last.