Right this is exactly what happened with the new sesame laws. The government declared sesame as an allergen and enacted heavy fines if it was undisclosed. This lead to manufacturers adding sesame because they couldn't guarantee they were sesame free.
do you have an example of this? it feels like a suboptimal response even given the stupid, heavy-handed legislation you cite.
"May contain" labeling seems like the better solution to this problem. This should be allowed for allergens that are present in the manufacturing or packing facility but not intended to be ingredients in the product.