The Nanhai No. 1 route is from China to Southeast Asia and up to India, and the ship's iron ingots may serve as ballast, and the most likely end customer is Southeast Asia. Because Southeast Asia has always been short of iron, for example, the archaeological excavations of iron tools in Vietnam were basically imported by the Han Dynasty. Han Dynasty Cultural Relics Unearthed in Southeast Asia and the Maritime Silk Road of the Han Dynasty - Nanchang Han Dynasty Haiyang Marquis Site Administration.
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If you take that the Arabs sank in Europe and that there were a large number of iron tools in their merchant ships, it may be possible to guess that this was the basis for the export of iron tools to Europe.
But one would not think of it that way if you look at the price of iron in medieval Europe, iron was so cheap that there was no price difference to drive Arab merchants to transport iron from East Asia to Europe. From South Asia to Europe, ships could only trade by land, so only silk and spices, which were light and expensive, could be profitable enough to support long-distance trade.