That sure is a big a web page for having no table of contents!
There’s a ToC on https://leanpub.com/phptherightway but I can’t link directly to it as the in-page link uses JS. (I’m on mobile though, so I can’t read the source. Maybe there’s an anchor someone else could link to.)
To answer the immediate question, I had a look and nooope, no <a name="">, not even <a> anywhere, that I could find. However I just (begrudgingly) realized this is somewhere text fragments can shine: https://leanpub.com/phptherightway#:~:text=Getting%20Started
To answer the bigger-picture question, the first thing I see (the above-the-fold part) upon loading the page (on both desktop and mobile) is a stylized ToC.
I'm not sure what you're seeing, but for me the page starts with a massive ToC. On even smaller screens it turns into a button fixed at the bottom of the screen that opens a ToC in an overlay.
There’s a ToC on https://leanpub.com/phptherightway but I can’t link directly to it as the in-page link uses JS. (I’m on mobile though, so I can’t read the source. Maybe there’s an anchor someone else could link to.)