If chametz can be batel before Pesach, why don't we buy (before Pesach) any commercially produced product with year-round (i.e., not Pesach-specific) kosher certification which does not list chametz ingredients?
Is this just another case of "Jews are very particular with kashrus on Pesach, beyond the letter of the law", or is there something more to it? And if the former then is it binding? — although of course CYLOR for practical halacha.
Here's an example to work with, for the sake of argument. Suppose a chocolate has the following listed ingredients: sugar, chocolate, milk, cocoa butter, cocoa (processed with alkali [i.e., "dutched"]), milk fat, lactose, soy lecithin (as an emulsifier), PGPR, and artificial flavor.