I have yet to see anyone counter argue the point I made about being able to fly HKG/ANC or even FRA/HKG two crew
Ok, I'll bite and try....
HKG-FRA:
Sign-on is at about 2340 local, therefore max FDP (2 crew) is 11 hours. The FDP required for that flight is about 13.2 hours, so 3 crew ULR FDP (13 hours) is insufficient: you need four crew.
The rest in FRA is over 30 hours, so the available FDP for the return flight is 13 hours, with a required FDP of 11:55, hence the provision in our FTLs that allows us to return to HKG with 3 crew.
If it were an acclimitised crew (say, based) that started in FRA, then they have about 13 or 14 hours FDP available, more than enough for the 11:55 required FDP (10:55 sector time), so they could do the flight under the leg stretch rules with 3 crew. For the return flight to FRA, they would have had over 40 hours rest, so that gives them an available FDP of 13 hours, again, not enough for the 13.2 hour FDP required, (nor is it enough to complete the flight using 3 crew ULR FDP of 13 hours) so four crew needed again.
That's my take on it - happy to be proved wrong.