I was surprised as well since majority of the replies on this thread advise against ever using miles in mySQUpgrade. I did have some challenges redeeming since AS # was associated instead of Krisflyer so had to switch and even then it showed ineligible. Had to contact support via chat who told me that I only changed the FF# for accrual and that they will need to change it for redemption as well. Whatever that meant, I was able to redeem miles for upgrade after that chat.