> Was the particleboard really the operative constraint? Or is the explanation about extra demand the correct one?

Probably both were contributing factors, along with a slew of other things.

This particular story does seem like it could be a folk-tale explanation, but it's not really about golf-carts - no one cares about golf-cart shortages. It's just a simple example of a broader issue for people to easily grasp. Even if it isn't particularly accurate, the same thing is happening in/across just about every industry