I think I misread https://practical.li/spacemacs/navigating-code/code-folding-methods.html as saying evil-fold was the default for your spacemacs config, but now that I think about it, it's pretty clear it's the default in spacemacs. So I misunderstood the relation between the spacemacs book and your spacemacs config (i.e., the former is not primarily documenting the latter unless it says so). It's an easy switch back to evil fold. Both the book and the configuration are great! It's a real upgrade to the spacemacs experience.