Their purpose isn't to get accurate information, they're there to give immigration authorities an easy legal way to kick someone out for something that would otherwise require a higher standard of evidence. I.e. anyone answering yes to that question is obviously a red flag but a former SS officer who writes in no can be kicked out by proving he knowingly lied on the forms due to his past as an SS agent without proving he was involved in or knew about the atrocities, which could be a lot harder.