Highly likely the U1 is just disabled in the firmware in those regions. (approvals will change over time - leaving the functionality out entirely would mean that it can't be enabled in the future) - also, having a separate SKU for a small segment of the market isn't desirable at all.
For a more definitive answer, someone would need to take one apart in one of the regions that have done so and review the layout of the board to see if the U1 has been removed. (you're not going to get Apple internal employees commenting on that here)