I have a partner flight on OZ metal booked through NH.

Segment 1 was already flown
Segment 2 is the return RT and not yet flown

I understand that the latest date that I can fly segment 2 is 1 year from Segment 1.
I want to change the date of Segment 2.

Is it a new rule that Segment 2 must be booked >96 hours prior to departure? I know that this is a rule for new bookings, but I always thought that changing a booking can bypass this rule.

https://www.ana.co.jp/en/us/amc/partner-flight-awards/
"Customers must change their flight award before the departure of their originally reserved flight and up to 96 hours prior to the departure of their preferred flight. If reservation changes or cancellations are not made by the departure time of the originally reserved flight, changes will not be permitted from thereon."