Currently, the catkin python install how to explicitly states:

To keep the user API clean, executable script names generally do not include a .py suffix.

However, the tutorials create nodes ending in .py. Now, the question is: which one applies?
If they indeed should not end in .py (which I personally would support because as the author of the catkin howto wrote, that's an implementation detail and not really relevant to the user), it would make sense if the Wiki Tutorials would either not create nodes ending in .py because most people will follow the tutorials when they create their own nodes or at least have a section about how normally you would strip the extension.

Edit: I just noticed that the catkin howto also proposes putting nodes in a nodes subfolder and other python scripts in a scripts subfolder which is also not consistent with the tutorials.