> Whatever metrics Apple is tracking on sales by country get skewed by this, tilting heavily towards U.S. and other countries and making them seem larger than they are, while also making the countries with typically weaker currencies and higher duties seem as smaller markets than they are.

They can most likely see analytics on which country is using how many of their devices. Where the device was bought would be just one metric. Where the device is being mostly used would be the more important metric here.