as-Salam alaykum, been a long time since last update.
Nuri Tabarsi rafidi muhadith in his famous book “Faslul Khitab fi ISBAT tahrif kitab Rabil ar-Bab” (p 32 manuscript) said:
“Second (point of view) that there was no distortion or deletion in it (Quran), and all that was revealed upon prophet Muhammad (sallalahu alayhi wa ali) is present between two covers on the hands of people. This point of view been adopted by Saduq in his “Itiqat”, Saeed Murtada and shaykh of Taifa in (book) “at-Tibyan”. And I don’t know anyone from the old (scholars) that agreed with them in it”.
Basically this scholar said that NO one from old shia scholars believed in protection of Quran like mentioned 3 do. As for them, inshAllah I will quote some sources that they did it only by taqiyyah.