If you assume people in the setting use nautical miles and round those off to exactly 6000 feet, you get this precisely.
Statute miles come from roman miles, which were originally 1,000 paces. Since different races would have wildly different step sizes, it makes sense that they'd be inclined to standardize soon than real-world people did. A nautical mile is one arc-minute latitude, or 1/21,600 of the circumference of the Earth. This makes it really useful for sailors and something everyone can agree on, so it makes sense to use it as a standard once it's decided a standard should be used (meters were originally set by defining 10,000 km as 90 degrees latitude).
Statute miles come from roman miles, which were originally 1,000 paces. Since different races would have wildly different step sizes, it makes sense that they'd be inclined to standardize soon than real-world people did. A nautical mile is one arc-minute latitude, or 1/21,600 of the circumference of the Earth. This makes it really useful for sailors and something everyone can agree on, so it makes sense to use it as a standard once it's decided a standard should be used (meters were originally set by defining 10,000 km as 90 degrees latitude).