Why Ibraheem was referred to as Ummah (أُمَّة) in this verse and why it was translated with other meanings?

My focus here is on the translation of the word Ummah (أُمَّة) in Arabic, by which Allah attributed Ibraheem in verse (16:120 ). As shown below there are different interpretation in its translation: > إِنَّ إِبْرَهِيمَ كَانَ **أُمَّةً** > Sahih international and Muhsin Khan > Indeed, Abraham was a [comprehensive] **leader**,... . - while Pickthall and Dr. Ghali used the word "nation", - Yusuf Ali used the word "model" - and Shakir "exemplar". All these words could certainly fit to describe this prophet (), but my question is: What is the actual meaning of this word in this context and why was it used as an attribute of Ibraheem and how -if it actually does- does it differ from it usual meaning? Which was discussed before in: - https://islam.stackexchange.com/questions/46012/what-makes-one-a-part-of-the-ummah - https://islam.stackexchange.com/questions/7570/what-does-ummah-mean-in-islam Or is there a secret behind calling Ibraheem "ummah"?