What is it that the angels (etc.) "concealed"?

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

1. The angels concealed their belief that Allah, the Most High, will not create any creation more honourable than them. [Al-Ḥasan, Abū al-ʿĀliyah, Qatādah]
2. Iblīs concealed his arrogance and disobedience. [Al-Suddī, Mujāhid, Ibn Jubayr, Muqātil] (Ed: on this view, Iblīs was included in the point because he was present with the angels. He is first mentioned in the subsequent āyah in which he refuses to prostrate along with the angels.)