Basically what he did what read about the "insight knownledges", (which are initially described in the Visuddhimagga, in a very loose way), and interpret them in whatever ways he sees fit, then proceed to see his, and everyone's life through the lens of that. He even diagnose everyone like an MD on his forums. (And incidentally, he /is/ a MD.)

You hear a dog bark and feel afraid ? Do you do meditation ? yes ? Surely you must be in a Bhaya ñana phase, and are on your way to enlightenment. Because bhaya = fear. Did you already experience that a few years ago ? did you go through this and that extremely loosely defined stages ? Then surely you are already a Sotāpanna and are headed to the attainment of once-returner.

Based on this he is an Arahant (because he says he cycled the insight knownledges 4 times).

But being an Arahat basically means being free of ill will, desire of the senses, and of a sense of self-existent self (and other things). It does not mean "just go though those phases, and that's it, that's his own reduction of the path to a few pages in the Visuddhimagga, which i would not even consider canonical personally.

> Are you basing this purely on reading about supposedly enlightened people getting angry or grumpy? That's a surprisingly common thing, actually.

People believing they are enlightened are common in some circles, yes, and it's always a red flag imo.

Yes, an Arhat does not get angry, that's in the very definition of the term: ill will has been totally eliminated. You cannot say you are an Arahat but you get angry, it would just mean you are something else than an Arhat, by definition.