Not sure if this was there before, but if I want to skip the seat choice at the booking stage, there's a note which states:
"You have not selected a seat. If you do not wish to pre-select a seat one will be assigned for you randomly from what is still available at check-in." So I guess that is a departure from the previous "choose at check-in" process?
Exact message I saw.
I'm not down on Jetstar for this, always thought the ability to pre-select at checkin was a bit of a loophole that would be closed one day, as it undermines the charging for the seat philosophy.
I ended up "stuck" in a middle seat in second half of the aircraft. It was nowhere near as bad as I feared or as people make out for a flight, flying time was a tad under 90 minutes. Happy to pay for seat selection on longer flights, but anything less than 2 hrs I'll suck it up.