It’s a deliberate choice in the article. I cover every single caveat with it explicitly. I also mention this:

> (note i could also have used a different romanization that renders し as "si", つ as "tu", and ち as "ti" for this article. i decided to not because everyone else uses romaji, and once you understand this point once, you shouldn't have a difficulty doing this in your head.)

I've never understood how people can claim that learning kana takes a week. It clearly takes more time than that, considering how similar some of the symbols are and a lot of them only differ by double dashes or a stroke (think nu vs me, ne vs re, ro vs ru, chi vs sa, and so on). Then there are the combinations and even if you managed to learn hiragana, you still have to learn katakana.

Oh and I forgot, you have to actually learn how to listen, pronounce and speak them, not just learn a useless romanization mapping. I've heard way too many English speakers just say the romanization with English pronunciation. At that point their learning efforts turn into self sabotage.

In total that's definitively a month of effort, albeit spread out over the first year of learning.

That’s just false, “si” is in the hiragana table as し. The romanization “si” is /si/ which is pronounced [ɕi] (or [ɕi̥] or some other possibility). This is basic Japanese phonetics.

If you fix all the errors that are in the article, at best there is an argument buried here that Hepburn romanization should not be used to teach Japanese to English speakers—but I think that point is really my own argument that I’m making with the fragments of the article that make sense.

Romanization can be more consistent with Japanese phonetics or it can be more consistent with English phonetics, and the Hepburn romanization is more consistent with English phonetics, which is why it’s a good choice for English speakers that don’t know Japanese, but a bad choice for English speakers who are trying to learn Japanese.