Example of situation where the rule would be applicable and problems that it solves:
Moria with Nature's Revenge, Rebuild the Town, Mischief in a Mean Way (all played in that order, of course).
Witch-king of Angmar is in play as long-event.
If not the rule then according to Annotation 26, hazard player could choose any order of effect and the copy of Moria would be effectively be [-me_rl-], [-me_bh-], or Wizardhaven.
Bag End with Chambers in the Royal Court is in play, News of the Shire is stored.
If not the rule then according to Annotation 26, hazard player could choose any order of effect and the copy of Bag End would be either [-me_bh-], or Wizardhaven.
Especially first example shows situation that is not intended in my opinion.
For refference:
EDIT:Annotation 26: If at the start of a player's movement/hazard phase, there are multiple
effects in play such that their net effect depends on the order they are applied, the
player who is currently not taking his turn (i.e., the hazard player) decides the order in
which they are to be applied. Once this interpretation is established, all further actions
are applied in the order they are resolved for the rest of the turn.
"Effects of cards played on other cards and limited to the other cards are applied as last and in order in which they came into play"
to
"Effects of card played on other card and limited to the other card are applied as last and in order in which they came into play"