For those who haven’t clicked through, they do say:
For purposes of this guidance, minor formulation changes should be consistent with the general factors listed below, as appropriate:
- Safety: the ingredient being substituted for the labeled ingredient does not cause any adverse health effect (including food allergens, gluten, sulfites, or other foods known to cause sensitivities in some people, for example, glutamates);
- Quantity : generally present at 2 percent or less by weight of the finished food;
- Prominence: the ingredient being omitted or substituted for the labeled ingredient is not a major ingredient in the product;
- Characterizing Ingredient: the ingredient being omitted or substituted for the labeled ingredient is not a characterizing ingredient; for example, omitting raisins, a characterizing ingredient in raisin bread;
- Claims: an omission or substitution of the ingredient does not affect any voluntary nutrient content or health claims on the label; and
- Nutrition/Function: an omission or substitution of the labeled ingredient does not have a significant impact on the finished product, including nutritional differences or functionality.
Still, I wouldn’t necessarily trust the safety part of that in terms of allergies, because 1) a person could be allergic to something that isn’t one of the major officially-recognized allergens, and 2) if you’ve ever worked on a job, you know that workers (humans) make mistakes all the time. I’m with @Wally, above; i.e., always best to cook from scratch if you need to be sure.
I think they should have required something like the addition of a simple sticker on the label that would say, e.g., The ingredients in this food are not as stated. Then people could at least have some warning, even if they won’t actually know what substitution has been made. But I didn’t see anything like that in my perusal of the linked info.
ETA: scooped by @knappa! I owe you a coke 
