That could be a cover plate as you suggested.
It can also be called an escutcheon or a , by most manufacturers, a canopy.

In some instances, the canopy covers up a hook which has a "ball" type socket that rest inside the canopy. Like this:http://doitbest.com/DoItBest/Main.as...=64&SKU=514632 This may be allowed by the manufacturer.


Here is another set of instructions for installing a fan:
Installing a Ceiling Fan

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Eric Van De Ven Magnum Inspections Inc. (954) 340-6615
www.magnuminspections.com
I still get paid to be suspicious when I got nothing to be suspicious about!