There is another possible reason to do this, and it is not pointless.

I don't know if this was already "done" in the other thread - my apologies in advance if it was.

Years ago some track racers tried to build a better mousetrap for the 1km time trial. In this event the athlete must start from a stopped position on the track, accelerate to top speed, and the time is taken at 1km. Lowest time wins. Gear selection is everything - a bigger gear means higher top speed, but slower acceleration. A smaller gear means faster acceleration, but a lower top speed...

Anyway, some guys (if anyone knows who please tell me) built their bikes with two fixed gears, one on each side of the bike. The right side had a low gear for fast initial acceleration. On the left side was a much bigger gear, but the cog on the hub was unscrewed almost all the way. This was legal because there is no freewheel, just two fixed gears.

When the rider starts pedaling, he's using the small gear. The big gear on the left, which has more leverage, starts threading its rear cog on. When it tightens, the big gear takes over, and the small gear is just along for the ride. So, you get a low gear for the start, and a bigger gear for cruising. You could get four or five turns of the smaller gear before the big one took over.

Of course, it only works once, which is fine for a drag-race type of application, but it would be foolish for riding on the street. Every time you decelerate, the big gear would start to unwind...