How did Ibn Mas'ud omit the Mu'awwidhatayn from his Mus'haf despite their being affirmed therein, and is this considered a textual flaw?

Scholars have differed regarding the authenticity of what was transmitted from Ibn Mas‘ud, may Allah be pleased with him, concerning the non-Qur’anic nature of the two surahs (Al-Falaq and An-Nas). Some, like Ibn Hazm and An-Nawawi, denied this, citing that the recitation of ‘Asim from Ibn Mas‘ud included Al-Mu‘awwidhatayn (the two surahs of seeking refuge) and Al-Fatihah. Others, like Ibn Hajar and Az-Zarqani, considered the possibility of its authenticity from Ibn Mas‘ud, interpreting it as having occurred before he learned of their Qur’anic nature, or before their widespread transmission reached him. However, the Companions and all Muslims have unanimously agreed on their Qur’anic nature. This consensus and the established Sunnah contradict what was attributed to Ibn Mas‘ud.