This has nothing to do with hamas.
In general, hamas is either a terrorist organization, or a military resistant. In both case, you don't expect anything from them. Most of the resistant groups or terrorist organization are not expected to tell the truth or be expected to respect international laws.
Isreal, is "recognized" state and government by many countries, they have trades and embassies around the world and part of the United Nations.
When they work so hard to show media "proofs" of a calender posted on the wall, a few guns in the MRI machine rooms, and no sign of it being the center of gravity and they get caught lying by their own videos they published then maybe we should consider them a terrorist organization as well and treat them like that. Maybe we should sanction any one sending them money.
If they are that confident they should show the world evidence, which regardless of what they found, doesn't mean they can commit war crimes.