Yeah, pretty much. I had to replace the pot on one of my controllers. It looked like someone jammed a screwdriver into it and smashed it. Fortunately, it used an off-the-shelf pot from Radio Shack and was able to solder a replacement in.
The first Famicom Vaus didn't have one, so I think Taito got complaints or something. The NES Vaus and the Arkanoid II Vaus have the pot for calibrating.