So it occurs to me, that if the definition of veganism is not eating or using animal products, then pleather is not really vegan. Given that pleather is plastic and plastic is made from oil, which is made from, you know, ancient dead plants and animals.
So if one were to take a reductionist approach to the question How Vegan Is Pleather, the only difference between leather and pleather is the amount of time the animals have been dead, and a bunch of processing.
Pleather is cheaper and easier to sew, leather wears better. Luckily I'm not vegan so I get to choose the material that works best for me. ;-)