Looking through the code I can confirm my suspicion the else starting at line 801 of exploration.gd in the AricsExpansion mod files is the part of code that recruits the rescued captive but doesn't seem to do anything to remove them from the world.
else:
rewardslave.obed = 85
rewardslave.stress = 10
globals.slaves = rewardslave
text = "$name observes you for some time, measuring your words, but to your surprise, $he complies either out of symphathy, or out of the desperate life $he had to carry. "