So, I think this is not freighter PXing
It IS freighter PXing. The "burnout" clause says after burning out, the rest of the time will be classed as "PXing", you are not legal to operate any longer because your FDP has expired.
This clause is not meant to be used on the freighter since freighter PXing is not allowed. In order for CC to roster you for this pattern they would need to ask you if you are willing to PX on the freighter.
Guys, in order for the company to stop abusing you contract, you need to uphold it yourself.