Please someone explain!

Cast iron is “seasoned” to make it nonstick. That means many layers of oil build up as a sort of polymer. The point is to keep it “dirty” in this way. Cleaning it down to bare metal means she’d be forced to re-season it, which can take considerable time/effort depending on frequency of use.

Isn’t the “seasoning” PFAS?

No, and nor is the teflon in the pans you’re thinking if. PFAS is a chemical used in the manufacture of Teflon (or was, I thought they’d stopped now) not teflon itself.
The problem with PFAS is accidental release and dumping.

PFAS is a chemical

PFAS is the term for the whole group of the stuffs called “forever chemicals” (for a reason). There’s not just a single one, but multiple, and as the specific ones and groups get banned, the industries move to use different ones, basically. It’s important to buy “PFAS free” stuff, any other labels like “PFOA free” can still mean there’s PFASs there, there’s just not ones from the specific variation

Damn, you’re right, I was thinking of PFOA not PFAS.

However, I think blanket avoiding an entire class of chemicals without evidence is an overreaction.

I think in the case of PFAS it’s very reasonable. There’s no real harm done in avoiding them except possibly making less money and having to figure out other ways to do certain things - which cannot even be compared to the the potential danger they pose to the whole ecosphere

That kind of thinking applies to any chemical though, surely

Only if they are persistent organic pollutants as well