The PLN is not the key to this accident . whether it is a hoax or not does not change the subsequent facts since they were apparently from the beginning intending to stretch the flight beyond legal reserves.
They could have put 3 alternates and 5h endurance and sign it as Jan Smith and the PLN would have been "perfect" for the ARO and ATC. No one on the ground knows how many (extra) tanks any aircraft carries in reality ( I have seen PLNs with 10h endurance on cross Atlantic Ferry Cessna172s) , and nobody can force you to land at your alternates anyway. ALTN are just there for info and the Endurance / EET part is only for SAR not for ATC. ( as someone said earlier those boxes are not even transmitted/processed to ATC)
It is the attitude of the Dispatcher ( and possibly the Captain) which is interesting in Miss Celia memo , not the PLN itself.