According to the service manual (printed, US edition), for US and .CA (canada) bikes, the interval is indeed 15K miles. For all other regions, it's 26K miles.
Why the difference? Who knows, perhaps the bikes are somewhat less powerful in the other regions?
It should also be noted that the actual for the adjustment instructions is on 2-24, not 2-22. The above image is from page 2-3 of the service manual. The dot falls under the 15K mile column.