Basically, it boils down to there being some things that should be defined in great detail, and other things that should only have vague definitions so as to leave ample room for creativity and innovation.
The term "3D rendering engine" is a good example of something that should be thoroughly defined. It is good to know exactly what somebody is thinking of when they talk about such a thing.
On the other hand, defining something such as what a game is doesn't really have a point and could actually do harm. A definition as basic as "A program, the purpose of which is to entertain or occupy the user" is entirely sufficient without serving constrain what one might create as a game. Creating a strict set of rules that a game must conform to, however, might serve to limit the imagination.
NOTE: This brings to mind something that I read a while back about game programming. Sometimes the people who make the best game programmers are those who are new to the subject and who's minds have not yet been clouded with notions of what they "can't" do.
I can only hope that this struggle to create a standardized game development vocabulary ends up being successful without going overboard.