The State of Palestine has two government at the moment which govern separate territories, just like Libya, Yemen, or China. Neither government of Palestine disputes the ICCs jurisdiction over Gaza. And unlike China there have been numerous attempts to unify the two governments, most of them were stopped by Israel.
I think the ICCs argument of jurisdiction is entirely reasonable, and consistent with how the court has ruled previously.
EDIT: Since this is Hacker News and we like nerdy details, I’ve linked below the 2021 ruling that established it’s jurisdiction of Palestine. The ruling was 3-1 and explicitly included the West Bank including East Jerusalem, and Gaza.
https://www.icc-cpi.int/news/icc-pre-trial-chamber-i-issues-...