AI设置告知翻译已禁用,但实际上已启用

I kind of understand that, but I thought SiteSetting.ai_translation_backfill_max_age_days is there to limit amount of history, and SiteSetting.ai_translation_backfill_hourly_rate is just slowing down things, right? If so, then why I got backfill, even that hidden setting was zero? That is what I don’t get now.