I'm probably nitpicking but I wanted to add more context to the highlighted.

In the WH method, you (can) also breathe in/out through the mouth, you also activate the sympathetic "fight or flight" nervous system. The difference with mouth breathing as described in the article, is that the WHM is a short term induced stress, which is highly desirable and beneficial ("hormesis" see #850029)

Sten Ekberg's YT video explains it very well.