Children and females are under-represented, all males are over-represented, and young men very over-represented.

That anomaly requires explanation.
The most likely would be that Hamas is lying about the status of its casualties.
Have you another?

Yes. In fighting units the world over, armies, navies, militias, whatever, men aged 20 to 29 are going to be over-represented. They are the ones doing the shooting and the ones who get shot at. Yours sincerely, Steve, Professor of Plain-As-The-Nose-On-Your-Face, University of the Bleedin' Obvious. What is it Musket calls you? Not Top Cat, is it?