The story forgot one important motivation for using 4D matrices (or more exactly, homogeneous coordinates), and that is the perspective transformation. With ordinary 3x3 matrices, all you can do is 3D are affine transformations, and both translations and projections (which is needed for eprspective) cannot be handled using only affine transformations. Anyway, any decent 'intro to graphics' course should explain this. Problem is there are too many books on the market along the lines of 'Learn Graphics using OpenGL in 1,2,3', which many students mistake as a scientific treatise on the topic.

There is freedom of religion in Belgium. You can practice any religion you want, as long as the people or organisation running the cult or religion abides by the law. The case brought against Scientology is not because there are a cult, it's because they have violated various laws under Belgian and EU law.