Just because it's inert doesn't mean it's harmless. I'm pretty sure that if you shove a wad of it in your windpipe, you won't last very long. Also go check out water poisoning.
I was curious about this study as well, both because the idea seems genius and wildly unsafe. I mean, I know teflon is inert, but really safe for consumption in quantities required for satiation? I googled the paper's title, and here it is: https://pubmed.ncbi.nlm.nih.gov/26810925/
The answer is that it's a study in rats, seemingly (from the abstract) a very successful one. Probably a bad idea to introduce that amount of "forever chemicals" into the environment, but the central idea seems pretty sound.
This is a case where conventional wisdom on HN is wildly out of sync with actual science.