The "may contain" line is not the part that the FDA takes issues with. From the source complaint:
> The Brownberry brand Whole Grains 12 Grains and Seeds RTE bread loaf product is misbranded for a similar reason; the product label includes walnuts, almonds, and hazelnuts in the ingredient and “Contains” statements; however, these nuts are not ingredients in the formulation of the product.
Emphasis on "Contains", which is a separate line on the packaging from the "may contain" line.
It isn't part of this complaint, however the FDA regulation explicitly says that labeling food with "may contains" is not good enough for major allergen cross contamination, which is why companies added them to the "contains" section, and why some companies are actually mixing allergens into he ingredients so they can legally add them to the contains section. (In this case, the bakery appears to have just added the allergens to the contains section without actually adding them).
The FDA should either 1) Allow the use of "may contains" for major allergen cross contamination. Or) Create a new category, such as "Possible cross contamination" that would be considered good enough. This would remove the incentive to deliberately add allergens while allowing proper labeling.
However, there are some lobbyist groups that want to force companies to use separate factories for any foods that contain major allergens, making those foods cost substantially more than they do now to produce. So the of us without allergens can either eat tasteless sterile food (likely leading to more folks with food allergies do a lack of exposure), or to pay out the wazoo for the privilege of eating normal food.
> FDA officials acknowledged Tuesday that statements that a product “may contain” certain allergens “could be considered truthful and not misleading.”