Maybe. On the other hand, unless Harry has decided to start lying to us about what it is he's actually doing, what he did, because it's what he chose to do, and thought he did, was condense gravity onto a small area. He's never made any mention of black holes or such.
Also, a tiny black hole wouldn't necessarily have any more gravity than anything else. A black hole as massive as the sun wouldn't change the gravity of the solar system at all. A picogram black hole would be no different than a picogram anything else.