My point is: The bad example does something, which is extremely inefficient but it just works. It has no side effects concerning security. All files are parsed by PHP, so no unparsed configuration files can leek.
The "good example" only handles requests to the FastCGI instance if the file or directory can not be found by nginx. This is clearly not the same although the whole intention of the pitfall site is, in my eyes, to offer exactly that: A naive, inefficient way to achieve things and a professional, tested, reliable and secure way. It's the first URL given in Debian's default config and possibly the first place a user will look like searching for help.
Proxying everything is certainly a bad idea; proxying too less is disastrous in terms of security. This should be pointed out in the wiki in big fat letters. Or better, let's come up with a better example of how to proxy a bare minimum.