Avios are convertible so you can move them forward and backwards as you please, and I would suggest doing so to take advantage of the arbitrage (in terms of seats open).

I've seen BA LHR-SIN on Club Suite open for redemption in AY's programme that were not available on BAEC. And of course the stuff on QRPC that BAEC can't get their hands on.

Ironically the democratization and increased appeal of Avios with uptake across OW means you're pretty much not stuck with BA's own programme in shopping around for the flights you need. Of course, if your flying is mostly short-haul you are probably best placed with BA still.