Perhaps someone was making mods that would float certain raid members throughout X number of parties. For instance, If party A has a certain number of members below a thresh hold hp, then the highest life member would be switched out with the shadow priest/imp LotP druid to heal them up. That would be unbalanced.
Is that what they are trying to prevent?
Things like that or having one person spam-click dispel magic on one raid frame, and some script just cycles members into that spot (aka: decursive)