At CX, no good deed goes unpunished.
But hey as you were helping out, unaware of any implications of AFTLs, wanting to get back to go home on days off, blissfully ignorant of the safety of the other crew and pax no doubt the CN will be suitably rewarded.
If the CN had insisted that they would not make HKG then IOC would have put a plan in motion to move the ac forward, somewhere, and have a replacement crew avail.
We are certainly putting passing muppets to operate as CNs now. Acceptable divergence and ignoring some limits, then all limits appears to be common practise.