application of current source and current sink concepts
What you are describing is covered in "A' and "B" above.  Your description for a sink is different. "C" shows perhaps a more common and intuitive description.

This a good question as a good understanding is needed.  A current sink/source is not the same thing as a ground which can both sink and source current.  This is important as not all components can both sink and source and misusing them can lead to confusion.