yeah, 'bioplastic' was the word I couldn't think of at the moment.
As with all things 'green', biplastics and biofuels are not nearly as green as they want us to believe.
As to the OP, "vegan leather" is just plastic, or Pleather. A synthetic fabric and not leather at all.
"veg tan" leather is animal hide tanned by using vegetable -sourced tannins, such as oak etc. A true leather.