If you insist on not using interlining you should have let them know.
Those are common for difficult lightweight fabrics... I just think fresco it is not strictly necessary.
However, if the tailor will attach a canvass as well, then the interlining will give an extra stiffness to the shape.
It seems that your tailor had stitched the interlining, this is strange and probably that will be the "floating canvass", good luck.
I wanted a full canvas construction. I think the tailor is using this black wool product as a canvas. I am not understanding your interpretation.