This is the problem with rumour networks......the facts might explain what is going on as opposed to just some of the facts.
While the flight from A to B will show a variable reserve as a % on the CFP, the alternate fuel consists of; - Missed approach manoeuvre, Flight to alternate, Arrival manoeuvre, Approach, Landing, % variable. You will need to check their Fuel Policy for this. It will just show on the CFP as just one single figure. I'm quoting here from my current operator, maybe PNG is different but I doubt it. For as long as I can remember the variable % for the alternate has never been tabulated separately so maybe they are just catching up with standard ICAO practise.