that chunk (occipital lobe) of the brain isn’t necessarily just turned off,

No it's literally just people blind due to issues with the brain not just the eyes, it says that in the article.

But without ever having visual input, it can't produce a visual hallucination. The brain wouldn't have any frame of reference and it's not like a "dark room" where you're still trying to see and experience a blackness, with that kind of blindness from birth there is just nothing, not the absence of visual input, the complete ignorance that a visual field exists. That's why some blind people still "stare ahead" they were likely able to see at some point or have some functional vision. 100% blind from birth and the eyes move independently and randomly. That person never learned to coordinate their eyeballs as an infant, they've never had any feedback.

(Pre-emptive edit: do not assume anything about someone else's ability, crazy fucking shit exists. Like, "blindsight" is real. Super rare, but sometimes someone just doesn't conciously have vision, but if you chuck a wrench at their head instinct takes over and they duck. That does not mean someone is "faking it")

The brain isn't just going to let the occipital lobe gather dust, it's going to repurpose it to handle something else like how a split brain patient who was young enough for the procedure to retain the brain plasticity necessary to form a second language center on the other hemisphere.

If anything that is where protection is coming from, the brain has a pretty big chunk to fill in defecinicies elsewhere.