Halliday & Matthiessen (2014: 382):
With only rare exceptions, all Qualifiers are rank–shifted. What this means is that position following the Thing is reserved for those items which, in their own structure, are of a rank higher than or at least equivalent to that of the nominal group; on these grounds, therefore, they would not be expected to be constituents of a nominal group. Such items are said to be ‘rank–shifted’, by contrast with ranking ones which function prototypically as constituents of the higher unit.