The Borg have been retconned from the beginning. Originally they were meant to be insectoid aliens, but then that was changed due to budgetary restraints to humanoids with cybernetic enhancements. In the episode where the Enterprise first encounters the Borg they do not attempt any assimilation of humans, and that attribute is only added in later episodes. So the Borg have assimilated new attributes throughout history, with First Contact continuing that noble tradition.
Sounds like heartbreak to me.