Redundancy in find_package(COMPONENTS) and catkin_package(CATKIN_DEPENDS)?

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As I'm debugging an error with .so dependencies, I've began to wonder about find_package() and catkin_package(). On the Wiki here it says:

# Get the information about this package's buildtime dependencies
find_package(catkin REQUIRED
    COMPONENTS message_generation std_msgs sensor_msgs)

## snip

# Declare that this catkin package's runtime dependencies
catkin_package(
   CATKIN_DEPENDS message_runtime std_msgs sensor_msgs)

OK, so it's compile-time versus run-time dependencies. However, if I look at the auto-generated help here it says:

• CATKIN_DEPENDS (list of strings) – a list of catkin projects which this project depends on. It is used when client code finds this project via find_package() or pkg-config. Each project listed will in turn be find_package-ed or is states as Requires in the .pc file. Therefore their INCLUDE_DIRS and LIBRARIES will be appended to ours. Only catkin projects should be used where it be guarantee that they are find_packagable and have pkg-config files.

Now this says "Each project listed will in turn be find_package-ed", so it implies that catkin_package() does a second find_package() as the find_package(catkin COMPONENTS), according to the documentation already does:

Instead of using find_package on those packages, if you specify them as components, it will make life easier.

So, what actually is the definitive description of what they do?