That seems like a pretty unfair summary. The author is a high school math teacher and the audience is clearly relatively non-technical. But I didn’t know that

That seems like a pretty unfair summary. The author is a high school math teacher and the audience is clearly relatively non-technical. But I didn’t know that rational tetrahedra (dihedral angles all rational multiples of π) were classified in 2020 https://arxiv.org/abs/2011.14232 https://arxiv.org/abs/2011.14232