I succesfully changed my awards (booked before 1Apr, and frist segments coming).
1st award involves a shorthaul LH flight.
I change that to 1 hour later flight. get approx 10000JPY refund.
Now, I may change that flight to 1 hour earlier flight without fee :-)

2nd award involves a shorthaul LX flight. I changed that to 2 hour later flight. I got refund.

As you may guess, I didn't touch longhaul NH flights to/from Europe.