As pointed out elsewhere, taco beef shouldn't be expected to be near 100% beef. Adding various seasonings and spices is what makes it "taco." Your linked artic

As pointed out elsewhere, taco beef shouldn't be expected to be near 100% beef. Adding various seasonings and spices is what makes it "taco." Your linked article makes the point that other chains hit the expected values for prepared chicken, Subway was an outlier.