Could be, but then why did he think he could control a star born?
Justin thought he could control a couple of kids, and bend them to his designs over time, leaving them open to enthrallment. And the more I think about it, the more the "enforcers" explanation smells fishy. More likely, they were being developed for their potential regarding the Outsiders, since we know Justin had those connections.
What if the enthrallment of Elaine and He Who Walks Behind being sent out have more to do with each other than has been previously reported? We know that HWWB is called via a ritual, a ritual for which timing is crucial. Perhaps involving star borns in that ritual yields another result that Justin was seeking. And perhaps, since his plan to perform a ritual with his apprentices fell through, he had no choice but to send HWWB after Harry, because the clock had already been set in motion.