UMLR — Why is Association.memberEnd ordered?

Association.memberEnd is specified as ordered but no rationale for this is given.

Possibly there is a requirement that a refined association's memberEnds be positionally consistent with the refining association's memberEnds. But there is no text or Constraint for this.

A mismatching order can generally be fixed-up, but in the unusual case of an N-ary association where at least two unrefined memberEnds have the same type, positional equivalence is perhaps necessary.

If the order is significant, is there a graphical policy for defining the order?