I actually don't see anything "attached" to this message.
In any case, yes, it is very common to use Polymorphism. Most game objects will participate in the Update/Draw logic, so they will probably have a virtual Update and Draw method implemented, which happens to be different by different classes (like enemies, the player character etc).
Of course the real details change a lot by the framework used to write the game. When I create games in WPF, for example, the rendering is most of the time done using WPF data-templates, so I don't need any virtual method on the class for the drawing. I am also able to separate animations from the objects themselves, so the Enemy objects don't need a virtual method for the animation. Yet, the animations themselves are polymorphic.
See these articles to have an idea:
Shoot'em Up .NET[
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Writing a Multiplayer Game (in WPF)[
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And I even used games to explain OOP in this article:
Introduction to Object Oriented Programming (OOP)[
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It actually shows why it is a good idea to use Polymorphism (virtual methods) to make the game work.