I thought pretty much the same to start with but the relatively small increase in power reserve (up to 47 hrs according to Ranfft) didn't seem to justify the increase in complexity of design and corresponding increase in manufacturing costs so I did a bit of thinking around the subject.
To be fair the conclusion I came to was in part speculation on my part, but it was also alluded to in a number of the articles that I read at the time, and it does make sense.
Another aspect to consider though is that using two small barrels instead of one larger barrel provides a different set of options regarding how you fit all of the bits into the limited real estate of the base plate, and this may also have been a consideration during the design process.
Absolutely, the hairspring is the most delicate thing in the watch- when it comes to manipulation.
It's unlikely that the hairspring was like that before you removed the balance cock. It simply wouldn't have run. It can't get like that from a drop or even being thrown from a rooftop.
As I understand it, the Chinese movements often leave the factory unlubricated and even with manufacturing debris present. This was probably the cause of stopping.