Semolina Porridge vs. Bananas

Because there isn't a definitive, universally accepted "bad" ingredient. The composition is too variable.
The text above about the banana is meant to illustrate that not all perceived "bad" ingredients in compositions are actually that bad. (Whether this is actually true is not the point of discussion).
But in the case of semolina porridge, it wouldn't be such a big deal, as it shouldn't contain any significant amount of complex esters or natural dyes.