I think the SQ/TPR situation is slightly different. It is an unadvertised benefit of SQ F that you can use TPR as an arrivals lounge, regardless of any onward flights.
Hmmm, not slightly different, exactly the opposite! SQ recognise the F leg and allow access based on that, QF don’t.
Not a deal breaker, as I was aware before I booked, it just surprises me. To be fair though, my last QF flight was circa 2012 so it’s not something I’ve paid oodles of attention to.