I’m surprised that Hamas apparently did not retrieve the corpses (which are still valuable to them) for six months. My understanding is that information about where hostages are kept is deliberately decentralized to prevent any single leak from letting Israel know all their locations. Did everyone who knew that these hostages were there die? Or maybe the tunnel ventilation system was either insufficient or damaged and the air in that tunnel was unbreathable this whole time?
Edit: Also I’m not seeing this information on www.ynetnews.com which is the Israeli newspaper that OP’s article claims as its source.