Yeah, of course, simplified is the word.

But they list the most important parts for specific functions. You could make a comparison with muscle use.
For example: if you lift something off the ground (basically a deadlift), the most important muscle groups are those in your lower back, upper legs and to a lesser extent those in your arms. But that doesn't mean they're the only muscles you use meanwhile. There's so, so many other muscles that flex in the process. It's just that the first three muscle groups are the most important ones in that activity.


Who's Paul by the way?