The state planning process has tended to push orders for each five-year plan to the last year or so before the planning period begins. As a result, Chinese carriers have been challenged in getting timely deliveries of aircraft that have few or no early slots, notably new models such as the A350.
The 2010 order for 10 was an exception to the process driven by Airbus’s allocation of A350 development and production work to China.
Someone mentioned about doing more ETOPS tests. May be this route allowed for some tests to be done, but these are pure speculations from my end as I do not have any intel that Airbus did conduct such tests during this flight