Deduct Points for Reward Seat 10 months after booking?

As per title.

~300 days ago I booked reward seats SYD<>YVR.

Assumed Qantas took points at the time, but to be honest didn’t check. I earn/spend >750k points per year so my activity statement is busy.

Flight is in 4 days and today they debit points - luckily I had the balance!!

Why did they not deduct points at time of booking like every other time?

I have managed my booking several times in the last months and it was always showing as ticketed/confirmed?