Look at your facts.
Each object has Hardness
PHB/RC, including the bones in your body
A&E/DMG?/SW and Warforged are made out of Wood & Metal
MM3.
Do Humands or Warforged have a Hardness rating? No.
Does their corpses do? Yes.
So what does this mean? I'm going to put it this code-like to try and explain it.
Hardness is a property of [Object]. [Creature] extends [Object].
[Creature] is living, animated (by spells),
really animated (undead/golems) or otherwise able to take actions, and while they have an inherited Hardness Rating, it does not apply. This is the base rule observed in function and every single creature statistical listing.
Now [Animated Object] extends [Creature] and creates a new property called
Hardness. This is not the naturally attributed Hardness rating from [Object], this is an
Extraordinary quality only found in [Animated Object]. It's like saying Grease (the spell) works exactly like Grease (pig lard) and is flammable or Prayer (thing you do while SorO pwns you) cannot be done unless you are a spellcaster (thus capable of casting Prayer the spell), or Dragon (anything with dragon type) means Dragon (as in true dragon).
Naming synergies has
nothing to do with
rule functionality.
Into it's self, Animated Object's Extraordinary Ability serves as it's own case and point. You have as a written rule operating as an exception. Read it; "An animated object has the same hardness it had before it was animated." This is a rule overriding intended base rules and says Hardness is
kept, meaning yes it is considered lost upon becoming a [Creature]. And Technically, keeping this
Hardness into it's self is worthless as Hardness not observed. Which leads us to the FAQ entry on page 76 where specifically Animated Object's
Hardness is called into question and applies per standard Hardness rules.
So which Hardness are you talking about? Building a
body made out of Adamantine for a [Creature] to give it an armor bonus and DR or building an [Object] out of Adamatine to improves the existing Hardness rating for that object? Because when I said living creatures do not have Hardness, I was meaning [Object]'s. Because if the trait is ignored and none-existent until death, it's a little like saying I have 10 grand because I have life insurance which really isn't applicable since I'll never own or use it.