The solder mask on PCB's is not designed to withstand much force, the friction of tightening a screw on it will surely strip it away. It's really just there for the soldering step to keep things from shorting during the assembly of the board. Any time you have a screw that will overlap the traces, there should be insulation supplied.
I can't imagine why they used that screw on a smoke unit, there seems to be no good reason.