Validating a long-standing joke towards less skilled players and making it "official" is just opening a psychological can of worms. Especially when this game already causes stress in a half dozen other ways (at least) as it is.
Also, Iron isn't really "below" Bronze as it stands now. Rather, Iron would be the new Bronze, with S9 Bronze being the bottom half of what's now Silver. So while the Iron tier will be below Bronze in the strictest sense, they're not worse than what used to be Bronze because they still ARE what used to be Bronze. If that makes sense.
Besides, if Riot really did call it Wood Elo, then people would just have to find another name for the worst of the Wood Elo players.