User blog comment:IamJakuhoRaikoben/Chapter 373: Life or Death?, Review./@comment-24446496-20140228224759/@comment-7418318-20140302205945

Not entirely true. In the anime Angel attacked Lucy with Caelum during the incantation, but the attack was somehow deflected, so maybe the caster is protected during the incantation or at least during the later stages of it.