I want to know the answer to the following question:
What feature of the Birmingham Quran fragments' text make some doubt that it is older than other known versions of the Quran?
All the background I'm provided with is that "This is possibly the earliest extant exemplar of the Quran, but as the tests allow a range of possible dates, it cannot be said with certainty which of the existing versions is the oldest.". Is that enough to answer the question?