The answer to that is simply that it is a fit for quantifying a feat that is otherwise impossible. Destroying a black hole is as quantifiable through physics as is reality warping a planet from existence. In other words not at all.
For planets we would use GBE for such cases, but due to the fact that black holes lack GBE we just needed some other quantification and that was what it came down to.
In regards to mass-energy: Makes really no sense to use that, because it is not like converting mass into energy is what happens (wouldn't even destroy the black hole if it did happen) and results in a high end usually (not always). For creating black holes, similarly to all other creation feats, assuming that it was done through converting energy into mass is just mostly outlandish and unintended.
Essentially creating/destroying black holes is to be treated like reality warping feats or other feats that break physics. But since we don't have GBE available as a measure, we just approximate using mass.
Assaltwaffle said:
While we're here, maybe someone can answer a couple of black hole questions I have.
A.
B.
C.
D.
A. IIRC in the standard model of particle physics you can even assume all quants to be 0 dimensional points. Thing is that is not problem at all, because you never really touch anything. Basically all interactions in the world come down to interactions between the 3-D fields that that the particles produce.
Same for black hole: their sigularity might be a point of infinite density, but like for everything else what really matters are the 3-D fields it produces. There is nothing strange about that.
B. The definition of GBE is the energy necessary to move all the matter of the object an infinite distance away from its center of mass (to say it simply). So let me ask you: how much energy do you need to pull something out of a black hole? Right, black holes are unescapable in physics, meaning it is impossible.
So you can either say GBE is just undefined for black holes, because the defining scenario is not possible for any energy, or cheat a bit and say it is infinite, because any finite amount of energy will not be able to produce the result.
C. For the infinite density in the center you really only need a tiny tiny bit of matter. All other matter that you later on throw in will not be in the same infinitely dense point. However, newly added matter still adds to the gravitational pull of the black hole.
An aircraft is for example also not directly on earth, but on the great scale its gravitational fields also adds the earths gravitational field.
Or one could roughly say that what matters isn't where the matter is, but where the center of mass of the entire thing is.
D. It has lightspeed escape velocity at the event horizon, which in physics can not be overcome even if you use infinite energy.
Hawking radiation also doesn't escape black holes. It works by pairs of virtual particles being created just outside or exactly at the event horizon (spontanously), with one of the particles escaping away from the black hole without ever going past the event horizon and one dropping in it.
Due to conservation of energy one can already see that if a particle is simply created like that the other particle must have negative energy, to make it so that no energy is created from nothing.
Since the negative energy particle falls into the black hole, its energy aka mass will decrease by adding it, making the black hole shrink.
So hawking radiation doesn't escape out of the black hole, it just throws stuff with negative energy inside.
