Yeah, the example is wrong, and the explanation is wrong. <bdi> doesn’t do right-to-left layout, it creates a new context for the bidi algorithm. That way, things like punctuation marks align to the text inside the bdi, and not the surroundings.
@zbraniecki, do you have a good example in your toolbox?
The reason why that text is in English is to allow English readers to see that the characters are reversed. In theory. I don’t know that that actually works.