he's sayn from the backside, water travels in and thru the door rubbers when you wash or it rains. mdf will suck it up and the sound proofing matt you added will hold it like a sponge and possibly start to mold up. The wmdf wood will expand and fall apart over some time. some plastic like what seperated the metal door from the door panel is what keeps this from happening... nice clean install and painting of dash.
I see what your saying. I'll just remove it if its an issue, I put it in just testing how well it would work. Did help sound proof it but w.e Ill just take it out Thanks, was a lot of work doing that dash