"Not necessarily recommended" because the example config may not fit all needs. It's probably fine for home use and many other uses, but it may not be the best config for all uses.
There is no way UBNT or any other manufacturer can outline a best config, that's really what the language is about.
The example config is probably a good starting point however, and for the end user that doesn't understand exatly what it does or doesn't do - it's probably good enough.