It’s true there are variant Qurans and that it is highly dubious to consider the text we have today as being both perfectly preserved and a complete text as opposed to a partial record (potentially with multiple redactors).
The Uthman story is not uniformly accepted among critical scholars though.
Almost nothing from early Islam is established historical record due to the paucity of evidence.
The only sources we have for the 7th c are the Quran and Hadith and sirah-maghazi literature written down centuries after the fact. It’s more akin to the New Testament apocrypha in timing than the gospels. There are also a handful of non Muslim fragments that add insights (but often contradict the Islamic narrative).
Much of the sirah is obvious nonsense, and much of the plausible stuff seem to be exegetical rather than historical.
Early exegetes clearly don’t understand parts of the Quran, and seem to have invented narratives to fix the meaning.
The problem is it seems strange to accept that early “Muslims” (a descriptor that seems to be a later adoption) recorded the most minute details of Muhammad’s life yet also forgot to record how he interpreted a fair amount of the Quran.
Many popular and even scholarly texts will take things like the Quran’s timeline, occasions of revelation and historical context directly from Islamic theology.
Many critical scholars do accept the Uthmanic standardisation, but some put the process later and even have redactions continuing into the 8th c. Others suggest it might be earlier.
This may be of interest:
Variant readings: The Birmingham Qur’an in the Context of Debate on Islamic Origins, Times Literary Supplement, 7 Aug, 2015, 14-15
www.academia.edu
Also on the unreliability of the Islamic tradition and evidence for the late standardisation of the sirah:
According to various Muslim
sources Muhammad
"was born in the Year of the Elephant, or fifty days after the attack of the troops of the Elephant, or thirty years after the Year of the Elephant, or forty years after the Year of the Elephant Many traditions are recorded in Ibn N~ al-Din's Jami' al-iithiu, fols. 179b-180b:the Prophet was born in the Year of the Elephant, he received the Revelation forty years after the Elephant (The fight at - K.) 'Ukaz took place fifteen years after the Elephant and the Ka'ba was built twenty-five years after the Elephant; the Prophet was born thirty days after the Elephant, or fifty days, or fifty-five days, or two months and six days, or ten years; some say twenty years, some say twenty-three years, some say thirty years, some say that God sent the Prophet with his mission fifteen years after the Ka'ba was built, and thus there were seventy years between the Elephant and the mission (mab'aJh) of the Prophet; some say that he was born fifteen years before the Elephant, some say forty days or fifty days, some say thirty years before the Elephant, and finally, some say that there were ten years between the expedition of the Elephant and the mission"
