First question:
First call by Crewing at 08:30Z - has it invalidated any rest period? If yes you get 12 hours rest from 08:30Z.
Second question:
Why answer the phone before STBY started at 14:10?
Point:
Not sure whether the next day would have been a working day or Day off. If the stop downroute is now in a day off there are implications to that. Also if it's not into a day off then what was planned for the crew on that following day.
All these points are relevant in order to piece together a sensible picture.
A personal opinion is that such a late notice for such a major change should be asked from rather than forced upon the crew.
Sorry, not sure if it's legal or not. The big question is how close to a start of a duty can crewing change that duty to a huge extent?