"Combined with the geology and the peculiar chemistry of the cave’s water and air, the evidence pointed to a system that had been closed off since roughly five and a half million years ago."

That quote, from the AI generated article, simply asserts the cave was sealed, it doesn't explain how the cave came to be sealed, nor how it is that modern humans infer the cave has been sealed and for how long.

On the flip side, the wiki article for the cave mentions that new species arrived as recently as 2 million years ago...