On an article by Gerd-Rüdiger Puin

I have found an article in https://amp.theguardian.com/education/2000/aug/08/highereducation.theguardian , It says, > Dr Gerd R Puin, a renowned Islamicist at Saarland University, Germany, says it is not one single work that has survived unchanged through the centuries. It may include stories that were written before the prophet Mohammed began his ministry and which have subsequently been rewritten It also says nonsense like thet the Quran has been changed, > As years went by, the correct reading of the Koran became less clear, he says. People made changes to make sense of the text. Puin gives as example Hajjaj bin Yusuf, governor of Iraq from 694-714 AD, who > was proud of inserting more than 1,000 alifs [first letter of the Arabic alphabet] in the Koranic text. Did he really examine Sana'a Quran? He even said > There are dialectal and phonetical variations that don't make any sense in the text Can anyone tell me if Gerd R Puin has any authority in quranic study and regarding Sana'a Quran? As I know, the difference between the Sana'a Quran and the current editions doesn't affect it's meaning but this article is making me doubt. Also about alif, is this a vowel sign that was added later in quran by hajjaj?