Further datapoint.
I recently cancelled a QF F award (P class) SYD-HKG sector for 6 Dec using AA miles, to allow earlier travel by 3 days to see my family who were already on vacation in SE Asia. Alternate travel to BKK was in J on a 744 with SkyBed Mk1, but a day flight so OK.
(yes, I know. No greater love hath a FFer than to give up an F award for his/her family...

).
I was curious to see if the P award would show again for the flight concerned following cancellation, and it did not.