FDA says stop using all THC vaping products (fda.gov)

I wonder why no exemption was made for leaf vapes that simply cook off the THC leaving the benzene behind.

There are no adulterants in a leaf vape.

I wonder if anyone has looked at whether it is simply the heat causing the damage. I see 200W mod kits on the web, which is a lot of heat to be inhaling. Maybe some vape pens are missing a filter which cools the vapor? Or the vapor doesn't get cooled as much if the pen is used continuously and starts to warm up? Seems like an obvious possibility.