I've ordered various items, including large ones, from Ali (baba and express). The customs clearance is handled at the port of entry and unless you are buying something that is freight only, they should forward it straight to the local post office to be brought to your home.
The bit about the 15 days is time for you to inspect the product before you click the confirm delivery button. Soon as you click that, the seller gets paid and a dispute will be a lot harder to handle.