@
Vasqueztion seems to me that they put him aside
because he's too powerful to incorporates in their main plan, unlike the girls.
their next plan of some sort of genocide is an optional side plan anyway, doesn't matter whether it succeed or not. and it makes a nice distraction for the boy when they go ahead and lure the girls into another test.
though why they still insist on targeting the girls after they know the boy is that powerful is beyond me.
they just established that getting the girls isn't vital for their plan, so to go out of their way to pokes the dragon is just unnecessary.