The reason is that such information is useless. If someone has a sesame allergy, they can not eat the food that "may contain traces" anyway. So actually having a definitive boolean _hasSesame is far more useful information, and will lead to less accounts of confusion.

Just as an example, my son's friend is allergic. Can I, as a parent of a friend, give to this child food with the "may contain traces" label? Will every parent of a friend make the same decision? With the new labeling, the answer is much clearer.

They added it where there was none before. People with allergies to sesame were eating bread at Olive Garden and Chick-Fil-A just fine before this legislation and now they can't.

> Though it's weird that the FDA don't just allow a 'may contain traces' warning, many countries do

The FDA always allowed that. But by naming it a major allergen the "Contain" statement becomes mandatory, and the "May Contain" statement doesn't satisfy that.