The section on Gibson's Petra theory ends with the following paragraph.
'A significant linguistic problem with a Nabatean origin theory has been raised by Marijn van Putten, a leading academic scholar on early Arabic and in particular Quranic Arabic, who has argued in detail that the dialect evident in the Uthmanic rasm of the Quran (also found in the Sanaa 1 palimpsest, so predates canonization) is Old Hijazi and not Nabatean.'
This seems to assume that the overwritten version of Sanaa 1 is older than the Uthmanic, which became the standard. But all that can be inferred safely from the manuscript is that the overwritten copy of the non Uthmanic version was written before the top copy of the Uthmanic version. Sinai discusses evidence that the overwritten version was in fact later, and may have been derived from the Uthmanic version. (When did the consonantal skeleton of the Quran reach closure? Bulletin of the School of Oriental and African Studies 77 (2014) pp. 39-40. Available at https://www.jstor.org/stable/24692711 and https://www.jstor.org/stable/24692364).
According to al Bukhari, hadith 4987, Uthman ordered the use of the dialect of the Quraish, who, according to tradition, were the dominant tribe at Mecca. (https://sunnah.com/bukhari/66/9). Which implies that some at least of the components to be incorporated into his version were not originally in the dialect of Mecca.
Fernando