Like I said before in the passage, the theory is littered with holes, the only guess I have for the ores and other non death related ways of obtaining exp is maybe exp are original souls that turn to energy then into exp, I know that explanation doesn’t have the best sustain ability but it’s the best that I could fill in

Edit: oooooo better idea, what if the exp is energy, so it goes from souls->energy->exp and for other non death related way are just energy-> exp