McGee must be referring to raw lima beans which are the only ones that contain cyanide bound in a sugar compound, although the ones grown in USA and Canada have had the levels bred down to pretty low levels. It’s harmless on it’s own but when chewed it mixes with an enzyme in the bean that releases hydrogen cyanide. Heat destroys the enzyme rending them safe to eat after cooking.
What I love about SVing beans is once I figured out the times for each individual bean after a soak, I can put 4 or 5 jars of different types of beans in the water bath, turn it on, set the timer for the quickest cooker, and just leave them. I pull each jar at it’s time and voila, perfect beans that I didn’t have to watch on the stovetop. Very liberating.