User blog comment:B214/Chapter 496: Forward/@comment-7418318-20160801113150/@comment-7418318-20160801114156

He did say that, but that doesn't tell us whether the Historias are at the same power as their living originals.

When Lucy summoned 3 Spirits at once the strain on her was so much that she couldn't even move and yet the Spirits didn't seem any weaker than if she had summoned them solo.

But then Celestial Spirit Magic and Historia of the Dead are two different magics, so the question remains.