If they're shipping crates over to the US and sitting on the inventory then they're not doing arbitrage. That's vanilla reselling. They're even providing a service by offering considerably quicker shipping times.

Arbitrage makes money purely off of information disparities between the parties. The guy who is better plugged into the market is able to mark up items in the middle of a transaction without having to take on any risk or provide any service.

Arbitrage != asymmetric information. Arbitrage just means bridging different markets with different prices for the same item. The parties in one market may well be aware that the prices are different in another market, they just can't/won't/don't bother to access the other market.

Information disparity between parties in contrast is referred to as "asymmetric information".

The case of importing from Ali, holding inventory, then reselling in the US is still not arbitrage. Arbitrage is by definition riskless simultaneous buying and selling of the same product in different venues.

Since the Ali importer is buying and selling at different times, the importer is assuming the risk that the market clearing price in the US will change before their inventory can be sold.

One academic definition of arbitrage includes zero risk, but usually not in contexts where it refers to something that happens in the real world, perhaps given that it's impossible in reality.

Actual arbitrage is very rare in the real world. If you're holding inventory at all, you're not doing arbitrage.

Arbitrage can provide a service as well.

The problem with this would be shipping times. I'm assuming this set up would be to list items on Amazon that you can purchase for cheap on Aliexpress? If so, Amazon buyers might not be happy with long ship times from China.

You have to be a Chinese citizen to sell on Alibaba. They make you type in your Chinese identification number (whatever it's called) when you sign up.

Is there a market for Chinese identification numbers on Alibaba?

That's only to sell though - I mean buying there and selling on Amazon or similar.