Sadly, it is highly likely that he will be retconned, because at the end of the last published Heresy novel, Ollanius did not enter the ship, he is with Vulkan, speaking of the rise of a fifth god who will be linked to humanity. The one who did enter was Loken, this is curious because in the first novel of the Horus Heresy he mentions that he had a dream in which he was with the Emperor and his father Horus, he sacrificed his life for the Emperor, and seeing what is happening , it is possible that Ollanius will be exchanged for Loken. Still, Pius will always be the last gigachad Catholic.