I think Bob has me on ignore, but this is just wrong. We're in the murky world of what constitutes
deceptive advertising. At the extreme end, suppose Taco Bell created a soy/oat based filling that had the appearance and texture of ground beef. Suppose further that this "filling" had 1% pure ground beef in it.
The legality of how they advertise their product would depend entirely the exact phrasing and context. Technically, their filling
contains pure ground beef. The question is how many consumers looking at a picture of a taco with what
appears to be seasoned ground beef and seeing "contains pure ground beef" would reasonably conclude that 99% of the filling is really oats and tofu.
Being truthful is but one burden. It also must not mislead customers acting "reasonably" under the circumstances in a way that affects a material part of their decision process. If I sell a mouthwash that I say prevents colds, that would be an untruthful specific claim. If I sell a mouthwash that kills the germs that cause colds, that would be truthful. However, the
implication is that my mouthwash prevents colds, which is not true. This is the example
the FTC gives.
So, when Taco Bell says their tacos are made with a tortilla, lettuce, cheese and seasoned ground beef, that's truthful. The question is whether it's misleading. I happen to think it is. I make tacos using ground beef. After I cook the meat, I pour off the liquid since I can't easily separate the water from the fat. I then add various spices (chili powder, cumin, salt, paprika) and a wee bit of water. That's seasoned ground beef.
I don't add any oats, flour, soy or yeast. Some people add corn starch. So, reasonable people will disagree on their expectations of seeing "seasoned ground beef" in the advertising (the exact list of ingredients is irrelevant to the advertising).
Side Note 1: The retail price of flour is about 60 cents per pound. The retail price of ground beef is about $2 per pound. When you sell a bajillion tacos, 5% starches can be a significant savings.
Side Note 2: While closing on our house about eight years ago, I got to talking with the clerks about Taco Bell wondering how they could sell tacos so cheap. This person, who said he used to work there, claimed that the "taco meat" came to them dehydrated. He said they added water to reconstitute it. I make no claims as to the veracity.
Side Note 3: Think outside the bun? How about thinking outside the frigging tortilla?