Now that's useful advice. Hadn't even thought of that. In the event of a change, probably worthwhile checking the carrier's website before accepting through Qantas. Good tip!
Did you get an email from Qantas saying the time had changed on that day, but then the Finnair website additionally offered a move to the previous day instead of accepting the time change?
That's correct. Exact chain of events for future reference if anyone ever goes through the same thing:
1. Flight change email from Qantas regarding Finnair flight time change
2. Accepted change
3. Checked Finnair's website to see if seat selection is required and noticed they have a reschedule option
4. Meanwhile e-ticket from Qantas is issued for 1st flight change while I'm mulling over risking my OWCA
5. Selected a new flight on Finnair's website to avoid my 16 hour layover (changed flight to previous day)
6. Finnair page went to a "Please wait while we change your flight, don't close this page"
7. Started receiving mass e-ticket emails + "Your flight has been confirmed" emails from Finnair. E-tickets did not reflect the change in step 5, but the emails did.
8. Received a "Your flight has changed, please accept changes" email from Qantas containing the new flight change made in step 5.
9. Accepted flight change in Qantas MMB (which seemed to stop the Finnair spam, but I also closed the ever-loading page in 7 at the same time).
10. Received email this morning from Finnair saying "Unfortunately your flight time has changed" but it was just showing the flight change in step 5.
11. Called Qantas this morning to push through the e-ticket as I hadn't received it. Received the e-ticket 10 minutes after calling. All flights showing as ticketed in CMT.