The natural concentration of the weird high molecular weight fluorine compounds is exactly zero, whereas cyanide compounds are natural and show up in small amounts in many fruit seeds, a couple nuts, some root vegetables.
Its not physically possible to eat enough apple seeds to get sick, but if you industrially concentrate cyanide by a factor of a hundred thousand or so because its so nifty at plating metals and stuff, then that purified form will kill you.
Its kinda like ethanol, your liver knows exactly what to do with it in small rare amounts, and out in the wilderness its extremely hard to die of ethanol poisoning from eating too many over ripe berries, or at least you'd have to try really hard for a long time, but given some industrial processing assistance its been possible for humans to die of ethanol poisoning for the last couple thousand years. Very few alcoholics drank themselves to death in 50000 BC, likewise no human died of cyanide poisoning until the 1800s AFAIK.
Unlike cyanides your liver has no idea what to do with the fluorine compounds given that a human liver had never seen one until 1930s, so naturally a little can really mess you up.
I see where you're going, but I'm not sure long-term prior exposure to toxins necessarily dictates just how toxic they are. There are too many confounding variables.
There are plenty of never-been-made-before chemicals that are completely non-toxic and plenty of been-around-forever chemicals that are super toxic (ricin, botulism toxin, etc).
> likewise no human died of cyanide poisoning until the 1800s AFAIK
Cassava roots (tapioca) have been killing and otherwise causing problems for humans for millennia through cyanide poisoning. Bitter almonds have been causing trouble for almost as long.
