No. It's a spacer to be used where needed.

But worry less about shell clearance than Q. Q is the distance between the centerline of the bike (say the center of the seat tube or down tube) and some spot on the pedal (say the outer flat of the crank arm). It should be the same on both sides. Since the drive side has to have a place for the rings, if the arms have the same flare then the root of non-drive side arm will have to be spaced away from the shell.

But there's really no way to tell if the arms have the same flare, so you should measure Q on each side and use the spacer accordingly.