He didnt know she was going to be turned into a Hound in Extermination. This event didnt happen in the future timeline he was trying to prevent. He thought he could slip in and take all the O5 without any complications but Ahab, teen Jean and X-Force got in his way. Rachel had already been turned by the time he realized Ahab was turning X-men into hounds and he was under the assumption that Jean would be able to fix that which she couldnt