I account for this by recognizing that the festival season caused a migration later in the year. At that time their presence at the Temple site would have introduced them to the destruction for the first time, despite the fact the great quaking and tempests had ended eleven months earlier. I also account for the various appearances of the Lord to "other sheep," as well as the forty-day ministry at Jerusalem in my reckoning.
However, I do not think it important for someone to disbelieve McConkie/Smith. It is only important how one decides to read the scriptures. Borrowed opinions are just that. People need to read the scriptures and decide what they mean for themselves.