Please post the link to the manual or other documentation that says this. . .
The link posted is someone's personal article. Which is about an approach that i have never needed (but then, i've only been involved with the definition and implementation of a few hundred databases (not tables - thousands of them)).
Personally, i believe that proper design will almost always have the "primary key" jumping up and down making itself visable. Long ago this little "rule" was published about a primary key: "every non-key attribute "must provide a fact about the key, the whole key, and nothing but the key - so help me Codd