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The behavior you are describing here was identical in FileMaker Pro 11 (Advanced) and earlier versions. If you would like to see a change in this behavior, I would encourage you to enter this as a suggestion into our Feature Requests web form at:
Another workaround is to define a sort on the relationship itself.
list() function does sort according to the sort-order in Relationship-Graph!
Though for yours Relationship Contacts <-> Notes, sort-order should be
sort Notes by Notes::Details
Further on, there are several CustomFunctions available for sorting lists - ie on www.briandunning.com
And ExecuteSQL, in FileMaker 12, can produce the same list of values but use an OrderBy clause to specify a sort order.