I would have thought it was the sellers responsibility to get...

I would have thought it was the sellers responsibility to get the product to the market (smelter in this case).
What you are saying is contrary to what I read in the Investing News regarding the typical as posted above. But I could only find one snippet of information and I am not saying for a second that you aren't correct.
Much better for AVB if they do get an advance payment at the port as there can be weeks to months before the smelter receives and processes your shipment.

One day we may see an off take or two but hey, what's the hurry? The plant officially opens today.