Positioning crew home on a freighter after a duty should not be mixed up with, or used to rationalize, positioning crew on a freighter prior to operating a sector.
Anyone on the 744 who has had to endure a long two-sectors of positioning on a freighter to Penang or Hanoi (through SIN or CGK), 10 hours long, prior to operating the third sector back to HKG, to end a fifteen hour day, will know first hand, how debilitating and fatiguing that is.
To position someone for 10 hours in the back of a freighter and expect them to be suitably rested to operate the third sector back to HKG is to ignore the reality of fatigue. What's more, it is a travesty that the third sector is counted as a first sector as far as the flight duty day is concerned (as if the first two debilitating sectors did not exist!).
Positioning crew on a freighter, to operate a duty within the same duty pattern, should only be be done via a direct flight on passenger aircraft. If done on a freighter, then full crew rest in a hotel is the only way a crew would be fit and rested to operate.