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Obviously the real reason is so they could just reuse Chop's model with only slight modifications, but iirc its not supposed to be a chain, he's a rebellious son who wanted his OWN ramen shop!
I think they're just some kind of organic lifeform, and they use the robo arms for increased ramen efficiency. 
I just happened to notice them out of the corner of my eye while I was doing some quests in Blazewood. It is a neat lil' detail, also funny to see that Bangboos used to be lil' tin shitcans. 

I don't think WuWa has had an event like this before where even if you start within the listed timeframe, you can still miss out on rewards for being "too late". Even the past Lollo Logistics events you could wait until the last day and do in one go.