In what sense was the Qurʾān revealed in Ramaḍān?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. It means the Qur’an was sent down in its entirety during the Night of Decree to the House of Honour in the lowest heaven. [Ibn ʿAbbās]
2. It means the Qur’an was sent down "about" Ramadan, i.e. to obligate fasting therein. [Reported from Mujāhid, al-Ḍaḥḥāk]
3. It means that revelation to the Prophet (ﷺ) began during that month. [Ibn Isḥāq, Abū Sulaymān al-Dimashqī]