Others have noticed as well, including the Center for Science in the Public Interest (CSPI), who recently launched a class action lawsuit against General Mills alleging false marketing. They point out the protein discrepancy, and reveal that Cheerios Protein also has more sugar.
The sad part in all of this is that in an effort to gain market share companies can sometimes resort to trickery to fool consumers (the recent Volkswagen debacle is another great example). General Mills and other cereal companies need to focus on true innovation if they want to increase (or at least hold on to) sales. They can do it, but these kind of shenanigans are not the way to go.