How sound and accurate are the verses attributed to our master Ali ibn Abi Talib: "I am the one my mother named Haidara"?

Indeed, Imam Muslim mentioned in his Sahih that 'Amir, the uncle of Salama ibn al-Akwa', dueled Marhab in Khaybar. 'Amir was then accidentally killed by his own sword. Salama was saddened by this, whereupon the Prophet, peace and blessings be upon him, informed him that 'Amir's reward was multiplied. Then the Prophet, peace and blessings be upon him, sent Salama to 'Ali, may Allah be pleased with him, who was suffering from an eye ailment. He (the Prophet) spat into his eyes, and he was cured. He then gave him the banner. 'Ali dueled Marhab and killed him. Imam al-Nawawi, in his commentary on Sahih Muslim, mentioned that "Haydara" is a name for a lion, and that 'Ali was called by this name because his mother named him "Asad" (lion) at his birth, and that he intended by this to frighten Marhab. As for "I shall repay them with the sa' of the sindara measure," it means killing enemies extensively.