In fact, looking at Airbus's O&D spreadsheet, Asiana's original order of 8 x A358, 12 x A359 & 10 x A35K now shows as 21 x A359 (of which 4 delivered) and 9 x A35K. So it looks as though they also converted one -1000 to -900 as well.
So they really like their A359s. IIRC, the A358s were meant as 767 replacement, so I actually expected the A358 order to be converted into A330neo's. Perhaps OZ will place another order for 767 replacement aircraft, and use the additional A359s for expansion.
Conversion of one A35K to A359 may not seem significant, but it there have been a some conversions from -1000s to 900s while one would expect the opposite though.
146,318/19/20/21, AB6,332,333,343,345,346,359,388, 722,732/3/4/5/G/8,9, 742,74E,744,752,762,763, 772,77E,773,77W,788 AT4/7,ATP,CRK,E75/90,F50/70