It is a pretty good article but I have some nitpicks:
They say both that you cannot decide in a vacuum and fast fashion uses synth materials to make disposable clothing. I think given these two ideas, the carbon usage for one garment of wool vs one garment of nylon should include all the "waste" garments produced as well. Since, when you buy from a company that practices this, the impact is from the whole process, as they are keen to point out. That includes the sweatshop to landfill garments.
Personally I like not wearing a microplastics generator.