Is it definitively proven that Israel is Jacob, and what is the ruling on one who denies that?

Al-Shawkani transmitted the consensus of the exegetes that Israel is Jacob. Ibn Kathir adduced a hadith in which the Messenger of Allah, peace and blessings be upon him, addressed the Jews, asking them if they knew that Israel (Jacob, peace be upon him) fell ill and vowed to abstain from his most beloved food and drink (camel meat and milk) if Allah cured him, and they affirmed this. Whoever denies this matter, while being knowledgeable of the authentic hadiths, is considered a transgressor, not a disbeliever.