Because "Across our portfolio, DuPont’s use of other PFAS is a small fraction of the total PFAS used in the world." Meaning, they admit they use it in many of their products, but insist they aren't a major contributor without providing numbers. Legally defensible.

They even have a "current use" button on that page. Lo and behold the information is right before your very eyes.

Where do they claim that?

They never made fire fighting foam, and currently don't manufacture those chemicals.

https://www.dupont.com/pfas/historical-use.html