That was covered in the article, but as the author was already older than 30 years, it wouldn’t have been applicable for them. It also seems the Working Holiday visa is intended for “employment as an incidental activity of their holidays for the purpose of supplementing their travel funds” [1], whereas the author rather appeared to be looking for a “working full-time with some incidental holidays alongside” situation.

[1]: https://www.mofa.go.jp/j_info/visit/w_holiday/index.html