Stereotypes exist for everything. And in this case, the guy is only making identifying the behaviour with the stereotype, he isn't even using the stereotype to make biased statements about the characters.
That is a great reframing of Reishou's humanity. But pettiness comes from a place of weakness, where he doesn't truly believe himself to be above everyone else but nonetheless needs himself to be. That's just not Reishou.
It's just that he's been the one inhuman character of the series. Flipping that on its head in his final moments for no thematic reasons is just weird.