Okay in terms of philosophy sure you could maybe make an argument, I don't know.
What we can, however, say that is more tangible is that the make-up of Hawking radiation cannot depend whatsoever on the matter that falls into the black hole apart from three properties: mass, charge and momentum. Other than those three properties, all other information that crosses the event horizon is lost and can't escape.
So, if one black hole was formed purely from 1 kg of protons with 0 momentum, and another black hole was formed from 1 kg of positrons with 0 momentum, these two black holes would be indistinguishable from each other. There would be nothing that could be emitted by either black hole via Hawking radiation or any other mechanism that could allow you to deduce that one was formed from protons and the other from positrons.
It's in this stricter information theoretic sense that nothing escapes from beyond the event horizon of a black hole.
What we can, however, say that is more tangible is that the make-up of Hawking radiation cannot depend whatsoever on the matter that falls into the black hole apart from three properties: mass, charge and momentum. Other than those three properties, all other information that crosses the event horizon is lost and can't escape.
So, if one black hole was formed purely from 1 kg of protons with 0 momentum, and another black hole was formed from 1 kg of positrons with 0 momentum, these two black holes would be indistinguishable from each other. There would be nothing that could be emitted by either black hole via Hawking radiation or any other mechanism that could allow you to deduce that one was formed from protons and the other from positrons.
It's in this stricter information theoretic sense that nothing escapes from beyond the event horizon of a black hole.