The spray-on glue layer might harden the surface somewhat and reduce high frequency absorption to some degree. Maybe not so good for RFZ panels. It might not be much, you'd have to run acoustic tests. For bass traps, as you know if you've read the material provided here, paper, plastic or foil is lightly glued the front facing surface to enhance LF performance. The spray glue might work something like that.
Like Hexspa says, most of us use fabric. Really seems to work fine.