Normal pilot training does not involve testing aircraft limits. Stall training happens in a plane with a known stall speed and behavior. The quote is about finding that limit for the first time.
Well, the nice thing about most planes is that they don't want to stall, and most of the time the correct action to recover is "stop doing things and let the plane recover". It's when you keep messing with it that you make things worse and get toward unrecoverability.