Join Date: May 2004
Location: SIN (LEJ once a year)
Programs: SQ, LH, BA, IHG Diamond AMB, HH Gold, SLH Indulged, Accor Gold, Hyatt Discoverist
Posts: 8,817
I'm entirely guessing here, but maybe larger mileage transfers like that (300k or so) go through some extra validation to ensure sender matches KF account owner. SQ is quite strict on the program rules around that. YMMV.