Hi,
The page you linked to lists quite a few problems that you will have when you do this. If those don't convince you, feel free to do it. But read the instructions carefully, so that you know how to deal with the problems properly.
I've seen quite a few people do this and get it wrong. If you forget to remove the nested .git directories before checking stuff in, you get those fake submodules. When cloning the project that directory will simply be empty and thus the classes will not be loaded correctly. Debugging that can be quite painful, and it's easy to forget to remove the .git dirs every time you update your dependencies.
Regards,
Igor