[ His features seem to indicate as much, for a human, though he hasn't stated otherwise. To her understanding human children are less prepared, or so she'd been repeatedly told. It was possible he was different; most seemed to come from differing circumstances. ]

There is no satisfying answer to that, as we do not know the full process to which they operate. The closest we may suppose is that it is most likely they seek out those who may align strongly to what they individually stand for, but they don't look much further for suitability or compatibility in anything else given their dire state.