To be self employed you need to take risk, so zero clients & zero income would be the situation if you opened a shop.
What they don't accept is an employee who works for 10 companies pretending he is self employed. If you go to do work in an office using the companies equipment at the times they specify you are an employee. If you could send someone else to do the work, then you probably are self employed, think of a plumber you send someone when you feel like it.