And of course even once you get to high enough conviction to call it causation, it’s still liable to be overturned and to reveal itself as a mere correlation nonetheless!
Humans have never once “proved causation” of even a single phenomenon ever.
This is a straight up pseudoscience and in its purest form.
It is practically intellectual fraud.
"Correlation doesn't equal causation!" cried the internerds.
It doesn't need to. If you've got a set (P) of N people who consume substance X, and N people (Q) who did not consume substance X, and 100% of set P died within half an hour of that act, and 100% of Q are still happy little dandelions, that is an entirely valid scientific finding, and an entirely sufficient reason to stop the supply of substance X.
And this study does not prove anything about them being good for people.
Maybe instead of X USD on this study we should have spent that money on an actual green space somewhere...