hmmm, well I tried to re-create things from Reply#1709, but got a complete different experience.
Relationship is stored in prefs.ini, and actually applies to the slot. Now if you manually de-select any enemy, it goes back into the pool to the right which will also set its relation to "unknown". Thus, any new enemy will also have his relation set to default "unknown".
Randomizing opponents seems to screw that. The game will randomly pick any enemy but the relation will stay as it was before. For example, if I manually picked 9 opponents, set all relations to "friendly", then randomized opponents, I will 100% end up with 9 enemies set to friendly, though it might not be the one I manually filled into the slots.
That is, there seems to be no way to randomize relations as well. You either set all relations to "unknown" for all slots before you randomize, or you give some slots different relations and then randomize, you'll then already know the number & full scope of all relations, but you won't know which whom it finally will be (although you'll see it right on Turn1 except if it's "unknown")