My question relates to the following ayah:

O People of the Scripture, why do you argue about Abraham while the Torah and the Gospel were not revealed until after him? Then will you not reason? -- Qur'an 3:65

In e.g. Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs (source: Al Tafsir), we have the following:

Then Allah mentions their dispute with the Prophet (pbuh) in that they said they are of those who have surrendered to Allah and follow the Religion of Abraham, claiming this to be in the Torah. So Allah said: (O People of the Scripture! Why will ye argue about Abraham, when the Torah and the Gospel were not revealed till after him?) after Abraham. (Have ye then no sense?) that it is not mentioned in them that Abraham was Jew or Christian.

This puzzles me, as the Qur'an was also not revealed until after Prophet Abraham. I'm wondering how to make sense of this:

Question: Why is it relevant that the Torah and the Gospel were not revealed until after Prophet Abraham, but not the Qur'an?