I think wwa means 100% certainty that you'll stick to the precommitted course of action. But that isn't what people mean when they say "precommitment", they mean deliberately restricting your own future actions in a way that your future self will regret or would have regretted had you not precommitted, or something like that. The restriction clearly can't be 100% airtight, but it's usually pretty close; it's a fuzzy category.