I think we agree on rejecting the views of Abdullah Ibn Mas'ood ra on Al-Mu`awwidhatain on the basis of Ijmaa' opposing it. Don't we?
Assalam o alaykum, Allamah Sarfraz Khan Safdar mentions in Khazain al-Sunan, vol.1 p.99, that the claim that Sayyidina ibn Masu'd [Allah bless him and give him peace] didn’t consider Muawidhatayn to be part of the Quran is an outright lie. قال ابن حزم فى المحلى كل ما روى عن ابن مسعود من ان المعوذتين وام القرآن لم يكونا فى مصحفه فكذب موضوع لا يصح وقال النووى فى المهذب والسيوطى فى الاتقان وما نقل عن ابن مسعود باطل ليس بصحيح "Ibn Hazm said in his al-Muhalli [vol.1 p.13], "All that is narrated from Ibn Masu'd saying that the Muawidhatayn and the Umm al-Kitab (al-Fatihah) were not in his mushaf is a fabricated lie and not authentic". And al-Nawawi said in al-Muhadhab and al-Suyuti in al-Itqan [vol.1 p.79], "That which is narrated from Ibn Masu'd is false and not authentic." Mufti Muhammad Saeed Khan has mentioned in his lectures that there are authentic proofs which show that Ibn Masu'd considered Muawidhatayn to be part of the Quran. How could he not? To deny one letter of the Quran is kufr, let alone two whole surahs of the Quran. Mufti Zar Wali Khan mentioned that it was proven that he recited the Muawidhatayn in prayer.