But he's using Luma, which protects firm0 and firm1 and the latest update has already been proven to be safe for a9lh usersAgain.
That's like saying "well, you've got a decently reliable bullet-proof vest on; so come over here and I'll shoot you with a Desert Eagle!" While you are wearing the bullet-proof vest, that doesn't necessarily mean it's a good idea to do anything rash simply because of the fact. Correct me if I'm wrong, but boot ROM bricks are not recoverable with A9LH (at least, I think so). Just so you all know.