I shall create a mytholgical answer to the question:
Heavy braking causes the nuts to rotate forward from the top, thus tightening, rather than loosening, the axle when the nuts are on the right. Thus, the nuts are on the right. Were the nuts on the left side, the forces consequent to braking would loosen them.
CAVEAT: The answer is entirely false, because the axle nuts (unlike lug nuts or hub nuts on automobile wheels) do not rotate at all.
Honest conjecture: I shouldn't think left or right placement of axle nuts matters at all.
Corrections and clarifications welcomed!