So we had this conversation a few times on here (about the China Open with the Ko/Yoo vs. Cai/Fu where that controversial fault was called) and BWF has placed a new rule regarding neutral umpires. Here it is:

BWF Superseries Neutral Umpires
It was agreed due to problems with some tournaments in the Superseries failing to provide the full complement of neutral Umpires, to extend the support BWF already provide to Superseries Premier events to all Superseries tournaments.
BWF will now pay the full air fare of 4 nominated BWF Umpires to Superseries Premier (up from a contribution of $500 USD) and BWF will now nominate 4 Umpires to each BWF World Superseries tournament with a contribution of $500 USD. Hosts are still required to provide 2 CC level overseas Umpires and it was agreed to implement a ‘step in’ procedure that if BWF learn that a host is unable to provide the minimum requirement BWF will make such nominations necessary and withhold $US1,000 per Umpire to facilitate their travel from any fees owed to the host member association.

Glad to hear BWF is stepping up in this matter and doing something about it.