Yes, finally read the page. It is very poorly written.
Since I am on a Mac, all I had to do was pick Pd > Preferences > Path menu and then click "New..." and then Cmd-Shift-G to get a field where I could paste "/Applications/Pd-0.47-1.app/Contents/Resources/extra".
I am now able to find Help > Browser... > flatgui/ > knob-help.pd and it works without issue.
I believe the motivation for not doing this by default was so that people sharing a computer by creating multiple accounts on that computer could potentially have different library path configurations. This makes a lot of sense if you consider academic environments, etc. It was a simple enough setting to add once I realized what was required.