To be fair, Troll-blooded came before they made the Living Construct type. I imagine if warforged had existed before they made the feat, they would have mentioned it doesn't apply to them because they're constructs, even though they're "living" constructs.
However, since it's in Dragon 319 which was during 3.5, they surely knew of the Horizon Walker and that it could give immunity to fatigue. Then again, WotC has never been that careful with certain rule interactions have they? lol