Sure but there are always some columns of an entity for which UCs or PKs don't exist and which you know only one result will be returned.
Well, however the framework don't have to worry, IMHO, of these exceptions (uniques that don't seems to be), and the code of retrieve that from a collection is pretty simple.
In some cases perhaps you haven't the luxury of altering the schema too.
But the framework is extensible
. You can do that method if you want, extending your EntityClass or modifying the template.