Installation of a heavier section on the "high" or outside of a curve is fairly common since that side is higher due to superelevation. Over time the high side gets "curve worn" (the gauge side of the ball gets worn, and the low rail top becomes flat because it carries most of the load because of varying track speeds. Depending on the sophistication of the program of the RR, the high side may be transposed, and depending on condition, the low side may be cascaded down to the yards, or scrapped. On the Elk River Railroad we ran on some 112RE rail that had been transposed at least twice and had worn to a narrow head, maybe 2-3" or so. It looked screwy but worked.
IMHO track maintenance is 50% art, 50% science.