You are right. Those are the spots. And yes behind the fabric (felt) tape, in the indents you'll find the screw heads. Perhaps some mm down, left, right. So try again, you'll find them. And yes you need to loosen them in order to remove the speaker bar.
If I remember correctly I could see from the cabin where the screw is located in regard to the indent. But my memory is not so trustworthy the last years...
Seriously, how am I so sure?
Because I searched them on my Cargo. And found them
If you need new felt tape I have metres of it left. Greyish. So I spray painted it black.