Hi, author here.

This was actually a mistake. If you look at the OWASP cheat sheet today you will see that Fetch Metadata is a top-level alternative to the traditional token-based protection.

I'm not sure I understand why, but the cheat sheet page was modified twice. First it entered the page with a top-level mention. Then someone slipped a revision that downgraded it to defense in depth without anyone noticing. It has now been reverted back to the original version.

Some details on what happened are in this other discussion from a couple of days ago: https://news.ycombinator.com/item?id=46347280.