In fairness, he only explained why a vast vast majority of people don't float away. He didn't adequately explain edge cases like Joseph of Cupertino - https://en.m.wikipedia.org/wiki/Joseph_of_Cupertino
That sounds super reliable. ;0)
"Poisoning due to the consumption of rye bread made from ergot-infected grain was common in Europe in the Middle Ages. It was known to cause convulsion symptoms and hallucinations. British academic John Cornwell has suggested that Joseph had consumed rye bread (see ergot poisoning). According to Cornwell "Here, perhaps, lay the key to his levitations. After sampling his own loaves he evidently believed he was taking off–as did those who partook of his high-octane bake-offs.""
Eilmer of Malmesbury showed a bit more commitment to his flying:
> Eilmer said he had "forgotten to provide himself with a tail."