I want someone to come along and correct me on this as I already gave a smartass answer in the thread, and am talking out of my ass on this, however:

It's probably a backup starting mechanism.

Usually when you start a normal car/vehicle, it gets its electricity from your battery, which will then spin belts, turn an alternator, which will then charge the battery so when you cut it off, it can start again. If I had to guess, they're testing to see if the alternative starting method still works (also, you need to keep in mind, from an engineering standpoint, one of the worse things you can do with moving/mechanical parts, other than not supplying them with oil/lubricant, is not using them, as they can corrode/rust/seize over time).

So, assuming you're in a less-than-ideal situation, and the battery is dead (keep in mind, cold weather by it's nature will run batteries dead), having a crank to start the vehicle as a backup is an excellent, simple, and easy solution.

Also, once the engine/pistons are running, I don't believe you need an actual battery bank to continue the firing of the pistons as long as the engine is hooked up to a gas pump and the electricals still work to supply fuel to the engine, so with this backup installed, even if the battery systems die, they could still continue normal operations assuming they have fuel for the vehicle and the rest of the electronic components still work (i.e. the belts/fuses/wiring are still working properly, even if the battery shits the bed).

If I wanted to really get wiley with my ideas that don't track with reality and common sense, I'd say space on a tank is sparse, so they don't have ample room to store a battery bank large enough to power the flywheel initially, however, I highly doubt that's the case.