On #Lost when Jack asks fake-Locke if the appearances of his father were also him, and he replies "Yes, that was me." ... That was a lie.
Not only is the evidence in Darlton's podcast, interviews, and commentaries, but in the show itself.
Christian appeared to Sun and Lapidus after smokey had taken Locke's form. It was explicitly stated that now that he had taken that form, he could no longer take another's.
He lied to Jack, because that's what he does... It's what Jack wanted/needed to hear.