People have told me the rubber puck compresses over time and require re-tightening otherwise it starts to rattle. I had initially thought the nut backs off (hence the serrated Nordlock washer) but if it is the rubber that compresses, the washer does nothing.
Basically since the nut needs snugging down periodically, this just allows easier access without dropping the strut.
Interesting. I was thinking that the puck's washer in the center was the only thing that contacted the shock rod/nut. I was thinking that my noise was possibly from the cover for that puck coming loose overtime, but I haven't had a chance to pull the front suspension apart to look. If the puck did compress, it should only move inside of the housing based on 034's diagrams on their site.