you have to remember Classical arabic written is without vowels. The way they tell which group wrote what, is the style of writing. They all used similar shapes for each letter, but the letters themselves stayed the same. Here in the US we call the word ABOUT (ab-out), in Canada that same spelling comes out to sound more like (a-boot).
It is tough to understand how this all works. But what I find fascinating is that IF this is from the time where the ayas were revealed, this could be one of the original manuscripts used to create the whole written work we use today. It does say however that it contains full Surahs, which leaves me suspect that this is from at least soon after.