Originally Posted by LHR/MEL/Europe FF

They do - but only to an extent, usually in the event of irrops.

SQ doesn't take complete control - for example if you want to cancel the ticket and get a refund, or you want to 'upgrade' a mixed class award where you accepted a lower class of travel due to availability at the time of booking. Those types of things are all referred back to the original ticket issuer.

The same with your case. The travel issuer has 'paid' SQ for a certain set of flights. SQ isn't going to touch that unless they have no choice (like IRROPS).