However, Sanad’s investigation shows that this is simply the access hatch for a water reservoir that the hospital uses to fill therapeutic pools for amputees, water the grounds, and a reserve water source in case of emergency.

Sanad analysed satellite footage and archives of the hospital’s construction and spoke to one of the original engineers who built it.

It's pretty in depth.

However I have two problems with this logic.

1. Israel did not confirm the existence of tunnels at that location, which would have been an easy thing to do with a camera and 2 minutes.

2. This isn't exactly proof that those areas weren't repurposed for tunnels. Just that what Israel thought was a tunnel was not. Which is more of a problem of how the Israel military is assuming too much and bombing people in the process. While processing their assumptions like fact.