After QF and EK started their partnership, there is no way for anyone to book a JQ flight to SIN connecting to a BA flight to LHR. In the past DRW pax could connect to QF Europe services from SIN. Now that option is not possible. Go on qf.com and they force you to fly DRW-PER-DXB-LHR or DRW-SYD-DXB-LHR which is a massive backtrack.
Plus Silk Air is a full service carrier and offers connections all over Europe and Asia, I'm sure plenty of QF pax would have shifted to them. So for QF to blame Silk Air and Air Asia is rubbish - they do not offer any options for pax to go anywhere ex SIN anymore. It's like the retimed QF72 to arrive in Perth at 4am. Introduce a flight with a lousy arrival time and no feed, then blame external factors for the route's demise.