Hamas has indicated it is currently unable to identify and track down 40 Israeli hostages needed for the first phase of a ceasefire deal, according to an Israeli official and a source familiar with the discussions, raising fears that more hostages may be dead than are publicly known.
Therein lies the problem.
I would say take it with a grain of salt, but there’s enough international scrutiny that I would say the list of missing is probably reliable enough. People in Israel are still protesting the Israeli government about that very frequently. Not everyone missing from October 7th has been returned, alive or dead. Many probably buried beneath rubble from IDF attacks, to be honest, since several were already confirmed killed by “friendly” fire.
Edit: to add, it is worth noting that Hamas is not the only group that participated in Oct 7 and took hostages. There are likely other hostages that they cannot account for because they were taken by other groups.