I think what you are missing is in making the assumption, implied by the article, that all police departments follow some sort of “standard police procedures”. I am skeptical that this is the case. Smaller towns are not likely to have the experience or resources that larger cities have.
A better question to ask would be, did the officers follow the procedures set forth by the City of Ferguson code?
That is what they would / should have been trained to do.
Maybe the municipalities adopt the City of St. Louis code. Being in the same state jurisdiction it would make sense, because they know what flies in that state’s courts.