I don't see what you think I got wrong about the story.
You realize the tunnels shafts are usually concealed right? They apparently walk right past them all the time. That's how tunnel warfare works. There are 500 miles of tunnels inside a 25 mile wide area. It's really inconcievable to you that there was a tunnel under this camp? That Hamas was literally using the tunnels because it was a humanitarian area, just like they do with every public institution, hospitals and so fourth. This is their strategy, Hamas and their loyal fans.
I don't find IDF's claim here dubious at all. It's a hell of a lot more credible just at face value than you're giving it credit for, at any rate. Seems obvious I'm talking to someone who only regards Israeli people as evil, attributes everything to malice.