What is the meaning of Ibn al-Musayyab's statement: "I do not lie as Ikrimah lied against Ibn Abbas," and how could such a thing come from the masters of the Tabi'in?

Ibn Hajar stated that the people of Hijaz refer to error as kadhib (falsehood/lie), citing Ibn Hibban's saying about Bard, the freed slave of Sa'id ibn al-Musayyab: "He used to make errors, and the people of Hijaz call error kadhib." He mentioned that Ikrimah was deemed trustworthy by many scholars, and Ibn Hajar narrated Ibn Abbas's commendation of him, where Ikrimah asked Abu Umamah ibn Sahl ibn Hunaif: "Did you hear Ibn Abbas say: 'Whatever Ikrimah narrates to you from me, believe it; for he has not lied about me'?" Abu Umamah replied: "Yes." Ibn Hajar added that the majority of imams declared Ikrimah to be reliable and used his unique narrations as evidence. Approximately three hundred men narrated from him, including Al-Bukhari, Muslim, Abu Dawud, and Al-Nasa'i, who all included his narrations. The general body of hadith scholars agreed on using Ikrimah's narrations as evidence, among them Ahmad ibn Hanbal, Ibn Rahawayh, Yahya ibn Ma'in, and Abu Thawr.