After getting some more wisdom from a wise colleague, I'm hoping the SIG contacts the Captain and notifies him of their oversight and the fact the line is a DP
Hopefully, the FO who gets it off Reserve notifies the Capt as well
Then both crew members can provide accurate reports to mgt and the union on how fatiguing the pairing is --- those reports get attention and provide important documentation on known threats to safety
Keep moving the mission --- safely!