PIL’s __init__.py is just an empty stub as is common. It won’t magically import anything by itself.
When you do from PIL import Image it looks in the PIL package and finds the file Image.py and imports that. When you do PIL.Image you are actually doing an attribute lookup on the PIL module (which is just an empty stub unless you explicitly import stuff).
In fact, importing a module usually doesn’t import submodules. os.path is a famous exception, since the os module is magic.
More info:
The Image Module