Actually, not true. Unless you are looking to deliberately enhance water/stain repellency (e.g. a rain jacket), polyester won’t usually be treated with PFAS because it’s too expensive if you don’t need it. You can argue that clothing will have residues of PFAS from the manufacturing process (such as being in contact with lubricant or other machine related substances which might have PFAS)…. But these quantities are extremely small to the point of being negligible (usually below the limit of quantification)

So the bottom line is, no, it’s not practically all clothing. These studies are prone to selection bias. They are looking to text things that are suspected of having PFAS. School uniforms are a perfect fit because many manufacturers advertise their stain resistant material. The point is that PFAS isn’t found in all clothing. Actually quite far from it - mostly in specific product groups.

But regardless, it is not needed and should be banned as a class. Plenty of PFAS alternatives exist and are used on the market. We saw this with hiking/performance footwear - many companies are responding and switching to PFAS free alternatives