Roster Disruption
If you're based in Nth America letsfly75, then they how can they justify extension of your duty on a roster disruption? Bit hard to assess without knowing your base (no need to tell), but unless there is a disruption whilst you are in ANC on the way home, how do they justify it? If they've canceled/changed the flight before you leave HK, then you should be PX'd to your home port. Being on the freighter or passenger should make no difference.
What next? Sorry, I know it's only day 1 of an 8 day pattern, but your flight on day 7 has been changed as part of a deal a G day worker made with us, so under the "roster disruption" clause, we can extend into your next 3 G days.
Don't even say that they won't try it on, if they haven't already.