Per Viajero: "IPC-SYD can only be done by backtracking via SCL (transit only); the mileage will be calculated IPC-SYD direct, not IPC-SCL-SYD.

Per rrgg: "The measured distance is between point of departure, stopovers, and destination"

Do these two statements mean the same thing, in that there's a stopover on Easter Island - probably for two - three days (anyone: is there more to do there than look at the big heads, and more time needed to do it?) and then the return to Santiago and onward flights to Australia count as a transfer assuming they can be booked to leave no later than 24 hrs after (re)arrival in SCL?

It matters as NOT counting the backtracked leg keeps it under the 25K miles flown award (via Webflyer's mileage calculator, so maybe not exact but there's a decent - 1K or so - cushion) but counting that segment would mean bumping up to a higher award level thus using up more miles.