This.

I would not transfer across separate tickets where the onwards flight is the long-haul, expensive, may require a new Covid test, and may involve lousy seats on a long flight, without allowing an overnight at SYD (and planning the testing in accordance). This, of course, obviates the baggage interline issue.

Most importantly, unless you are traveling in the next few days, schedule changes are routine and thus ample time to make your unprotected transfer may quickly dwindle.