The Mera Mera no Mi also inherited Ace' will when utilized by Sabo. I think there is a difference between an object (or even fruit) bearing the previous user's will/ambition or having his Haki specifically stored into an object for it to be unlocked later. Enma doesn't really use Oden's Haki, it just bears Oden's will/ambition (ambition is often used interchangeably with Haki). But we know that even a black blade like Shusui couldn't harm a logia when not amplified with the user's Haki, so it's not Haki (armament, conqueror's Haki) from the previous user in the literal sense that gets utilized in a fight.