I don't know why you people talk about that.
Let's just look at the manga.vol 13 chapter 117
Sandaime attacks Oro with Shuriken kage bunshin no jutsu.
Oro does his summoning toi shield himself.
Two coffins with writings (first and second) appear.
Sarutobi says he has to do something against the third one and does some handseals.
No third coffin appears. He says that the third one didn't work, it seems.
Oro doesn't even react to it. He is not bothered by it or anything. There is just no reaction from him. If he failed to summon the best shinobi there ever was, I think he would've reacted on it.
Maybe he didn't even try to summon a third coffin.
The manga doesn't show one, so why not.
"For Feanor was made the mightiest in all parts of body and mind, in valour, in endurance, in beauty, in understanding, in skill, in strength and subtlety alike, of all the Children of Illuvatar, and a bright flame was in him"