Wasn't where some info where Nasu said, what if Uryuu not screwed up, Gilles could have been summoned as Saber with Golden Rule?
Just a guess, but maybe where is Hero!Gilles, who is proper heroic spirit and could be summoned as saber, and where is Bluebeard!Gilles, who is technically not HS and could be summoned only if something screwed up.