I get what you’re saying but I’m pretty sure it matters in international law for additional charges against Hamas leadership. There’s, tragically, sexual violence in basically every conflict, and individuals who do it have committed a crime for sure. But proving it’s systematic and used as a tactic would make higher ups in Hamas guilty of (even more) war crimes.
So, it is important for prosecuting Hamas leadership that there be a proper, legal investigation and that it be proven to be either knowingly allowed or (even worse) ordered as a tactic.
Obviously, Hamas and Israel have both committed enough war crimes already that the senior leadership will likely be found guilty of something at The Hague (if ever arrested). But properly accounting for all of the war crimes is important for both justice and history.