If a food additive is "generally recognized as safe," food manufacturers do not have to disclose its presence. And there's a lot of bullshit allowed when it comes to marketing. Eater looks into "natural beef flavor" and what it really is.
As you likely suspect, given that McDonalds French Fries are legendarily "natural beef flavored," it doesn't have to contain any beef at all. But the FDA does regulate it.
According to Reineccius, "the flavor in beef is created during the cooking process. Food scientists identified the amino acids found in beef, added some very common sugars — starch hydrolysate — put it in a pot, added some citric acid to drop the pH, controlled moisture content, and heated it to the same temperature as meat. Then...*poof* we have meat flavor." As a result, that "natural beef flavor" may actually be vegetarian. Once a flavor is broken down into its basic chemical components, scientists can reconstruct it and add one food's flavor to another, creating that umami-like, "meaty" taste without the beef.
Here's a meaty mix for you: https://www.youtube.com/watch?v=izCmWxjnidc