What is the interpretation of Uthman's saying regarding Hajj al-Mut'ah: "But we were afraid"?

The hadith the questioner referred to is what Muslim narrated from Qatadah, who said: Abdullah bin Shaqiq said: Uthman used to prohibit Mut'ah, and Ali used to command it. So Uthman said a word to Ali, then Ali said: "Indeed, you know that we performed Mut'ah with the Messenger of Allah, peace and blessings be upon him." So [Uthman] said: "Yes, but we were afraid." Al-Nawawi is of the view that the Mut'ah which Uthman prohibited was the tamattu' in Hajj, and his and Umar's prohibition of it was a prohibition of preference (tanzih), not a prohibition of unlawfulness (tahrim); because ifrad (performing Hajj only) is better. And that Uthman's saying: "We were afraid" perhaps referred to the day of the 'Umrah of Qada' in the seventh year [of Hijrah]. Ibn Hajar is of the view that the narration: "But we were afraid" is shadhdh (anomalous). And it is possible that Uthman indicated that the original reason for the Prophet's choice, peace and blessings be upon him, to dissolve Hajj into 'Umrah in the Farewell Pilgrimage, was to counter the Quraysh's belief that 'Umrah was forbidden during the months of Hajj, and they were afraid of fighting breaking out between them and the polytheists.