Quoted from Rarehero:

I don't think so - Shadow's under the playfield magnet can stop a fast shot. The magnet on the Ringmaster's head on CV (hidden under the lid on his head) usually grabs fast shots. I get the feeling exposed cores were done to either show the player there's a magnet there and something cool will happen...or to prevent the wood from getting worn by the pull of the magnet. Shadow's often have wood wear where the magnet is..but had they put a strip of mylar there to begin with, it would have been fine.