Black holes are not made of matter… the matter has collapsed into pure energy. The form of energy is a mystery (it’s inside the event horizon) but since the gravitational field persists, it’s often referred to as pure gravitational binding energy. I graduated physics at Manchester Uni and I’ve still got a ‘preference’ to be as correct as possible when talking about BH’s and what they’re ‘made’ of. Kip Thorne also often refers to the stuff BHs are made of as ‘gravitational binding energy’ so I thinks it’s safe to do the same.
In GR, black holes have only three distinguishable properties: mass, charge, and angular momentum. If you have one made from matter, one from antimatter, and one from sufficiently concentrated light, all three are indistinguishable.
As I'm not a physicist, I wouldn't risk phrasing this as "pure gravitational binding energy" just in case this has a specific and different meaning.
I read the interior of an event horizon immediately causes problems with quantum mechanics' no-cloning rule, so I suspect the actual problem here is "QM and GR are fighting again" and we can't get any answer until we've resolved that.