I went through that last year on a flight... saw the outbound in F for not much more than the P fare, and the return was only available in P so picked that for the 200% bonus on one direction. Posted as 150% with paid C / flown F.

Had to argue for the bonus and was told that I had a C fare, so I was asking how it went in the F bucket even though C inventory was available. Luckily I had a screen capture of the booking page showing the 200% mqm earning breakdown so got the credit.