I don't know, but the "Read Online" button leads me to "https[://]talkpython.fm/books/python-in-production/#read-online", and that URL then tries to redirect to "https[://]talkpython.fm/books/python-in-production#read-online". (Notice how the last slash of the path is missing).

This forced my browser to reload the page, and it beats the entire purpose of anchoring and fragment-based navs.