This is completely false.
The IDF has never planned, approved, or carried out a strike in Gaza in which 500 civilians or anything near that number were anticipated to be killed. Nor was any credible claim raised throughout the war suggesting that an IDF strike had caused anything near that number of fatalities.
The filmmakers couldn't possibly verify this claim, there is no real supporting evidence, and yet they published it anyway. Additionally, nothing about the interviewee, not his service nor his role can be independently checked and verified.
No such strike was ever planned, approved, or carried out yet this is the claim the filmmakers chose to promote their movie with. Judge the rest accordingly.