The spin axis isn't a valuable reference since it depends on your frame of reference, which is a concept that gets rather ambiguous as you get close to a black hole anyway.
Plus you can just "rotate" a black hole to get it to have the same spin axis as another black hole. You can't "rotate" or "translate" a black hole in space to make the other three numbers change. Those require ingesting matter or emitting hawking radiation and that is the only thing that changes those properties.
Plus you can just "rotate" a black hole to get it to have the same spin axis as another black hole. You can't "rotate" or "translate" a black hole in space to make the other three numbers change. Those require ingesting matter or emitting hawking radiation and that is the only thing that changes those properties.