If a plant needs to be in the dark to germinate, covering with fine soil such as a seed starting mix is going to be much more effective than dark cloth.
Firstly the soil will hold more moisture around the little seed helping it to germinate. Secondly, when it does pop, the little plant will have soil and nutrients around it immediately to help it stand up and grow. If you were to have seeds start growing on the soil surface before you removed your dark cloth, they would be stunted trying to grow through the cloth.
The some types of seed that like to germinate on the surface with light also have a gel-like coating that holds water. This becomes evident when you first water them. Try this with Basil seeds and you will see what I mean. Otherwise, you're trying to improve on Mother Nature and that seldom works well.
I do sometimes put plastic wrap over a flat of seeds for the first few days to help keep moisture in the soil surface. After seeds start to come up, I mist with a spray bottle so I don't knock down the tiny new plants.
Good Luck, David
