When I am in doubt about the crediblity of a source I always go the primary source like the first two links in my signature. The second article was written by the researchers who developed the diet. The first link was written by a dietitian trained by those authors. Both say list corn under the "Suitable alternative low-FODMAP food source". Thus corn flakes looks okay. HOWEVER, there could be varieties of sweet corn that are high in polyols.
I have not been able to find a definitive source that says corn flakes are made from sweet corn. I suspect it depends on the manufacture. If you eat Kelloggs then perhaps you might call customer hotline to find out for sure.
Since the advent of this diet many individuals have prepared their version of the diet which frequently contains errors.
I don't pay attention to corn because of its high insoluble fiber content - it is not on my list of safe foods
-------------------- STABLE: ♂, IBS-D 50+ years - Science of IBS