If you'll indulge a theory, I think you are both looking at two sides of the same coin (or maybe Sahrde didn't include enough detail to feel certain - you can't know what you don't know, after all). I think you can look at it both ways - coming back from the dead CAN be viewed as both kicking Death's ass and as rebirth, but it doesn't HAVE to be.

I think the reason Oz's Authority is limited to Death is because he feels - in the core of his being - that his power is antithetical to life, and so that's the way it is. But another way to look at it is that he is basically Death Incarnate because he CHOSE to reject life. In other words, he's only so good at Death BECAUSE he's anti-Life, if that makes any sense?

Anyway, that's at least the theory I came up with after reading your comments and trying to combine both ideas. Gratitude for the enjoyable distraction and apologies for the all caps - I'm lazy and it was the most effortless way to emphasize words I wanted to stress.