AH should not be recommending speaker level attenuation and distribution. It is not elegant nor appropriate for a proper whole house setup where sound quality is important. Just because it is commonly done or relatively easy and cheap does not make it okay.
Adding resistors into the chain to impedance match and calling it "Protection Circuit" is hog wash. One might as well use high gauge speaker wire in that case since the net effect will be the same. If your insertion resistance (cable + "Protection Circuit") becomes comparable to the nominal speaker impedance, you can throw sound quality out of the window. More on this topic here,
Speaker Wire
As an alternative to the deeply flawed recommendation in the article, a better approach is to use a distribution amp. Something like this one,
HTD DMA-1240 High Efficiency Multi-Channel Amplifier The amp is great and does line level signal attenuation rather than at speaker level like the passive selectors in question.
I have used that HTD amp to set up a dining hall with 10 on wall speakers from Monoprice. It has been working flawlessly and without any concerns about sound quality or blowing the receiver due to an impedance mismatch created by a flawed solution.