Durability isn't quality, and quality isn't the only characteristic that matters in fashion.
Durability is a totally tangential metric though. It's more common to find delicate clothing, sheer fabrics, etc, in high fashion than it is in fast fashion, including in the T-shirt category mentioned in the article.
Veblen goods. Durability isn't the point, visible luxe is. Of course old money would say you can't fake it, and that suit from Gieves & Hawkes (before the stupid plc thing of course) is both visibly luxe and lasted your grandfather, father and you.
Durability is a totally tangential metric though. It's more common to find delicate clothing, sheer fabrics, etc, in high fashion than it is in fast fashion, including in the T-shirt category mentioned in the article.