"True heroism is remarkably sober, very undramatic. It is not the urge to surpass all others at whatever cost, but the urge to serve others at whatever cost." -Arthur Ashe
I didn't mean to imply an absolute cowitness, I was thinking more along the lines that given a normal low-as-possible cowitness, if the dot is roughly centered in the window the front sight will appear high above the rear notch by a distance that might become familiar to an experienced shooter. Similarly, if the dot is to the left side of the window, the front sight blade is probably just leaving the notch (dependent on the specific sight configuration and sight radius), and so on and so forth. The question then being what is the likelihood of recognizing abnormal iron sight alignment in the background of your mental processing while putting the dot on target as your primary sighting system.
In case a fuzzy picture would better illustrate things, consider the sight alignment below. If I saw a false dot on the left and real dot on the right but the dots themselves looked identical, the irons would give a strong indication which is the correct dot, and then I'd have the choice of shooting to that dot or transitioning to irons (on the chance that dot too could be false). Now what if only the false dot was visible, say the real dot was off the window as it were...might an experienced shooter pick up on the misalignment of the irons subconsciously while treating the dot as the primary sighting system? Maybe it's unlikely or unrealistic at speed, I don't know, but if we're looking for every clue we could give the brain that something isn't right, could there be a potential benefit to backup irons even on a training/competition gun...both to potentially help with recognizing a false dot and to train the brain what correct orientation of irons looks like when shooting the real dot in various positions.