I'm planning an ex-JPN DONE3, and I'm wondering about the rules regarding changing the date/time of the first flight.

The Wiki says that "For tickets originating [outside the Americas], changes to the first international flight and preceding flights are not permitted." But the OneWorld site's T&C's doesn't make any reference to the origination point and says: "Changes are permitted provided ticketed points remain the same. If the first flight coupon is being changed, and the fare level has increased since ticket issuance, the difference between the old and new fare will be charged."

Is it fair to assume that I can change the date/time of the first flight of an ex_JPN OWE (subject to any fare change in the ticket), and that the Wiki needs to be updated regarding this?