> But that said -- and as others have noted -- the explanation here is misleading, and that's because of the dependence on romaji / transliteration. Japanese conjugation is extremely simple, and the author is missing some essential context that would make it all much clearer. For example:

Doesn't going straight to kana actually kind of obscure the relationship between nomu and nomi that they both begin nom-?

> Doesn't going straight to kana actually kind of obscure the relationship between nomu and nomi that they both begin nom-?

No, because nom- is not a sound that exists in Japanese phonetics.

nomu/nomi share the initial の, and む/み are in the same column of the kana table (五十音/gojuuon).

Sure it is. It's just bound to a vowel.