That article seems wildly misinformed at best and AI-written at worst. Saying that humans evolved color and forward-facing vision just to detect snakes is ridiculous, and the claim that snake venom evolved after constriction (and has anything to do with humans) is definitely not the current scientific consensus. As it stands now, we actually believe that the lizard ancestors of snakes already had a basic form of venom, and the unique thing that the snake lineage evolved were hollow teeth for efficient venom injection. Because apparently the venomns within the venomous lizards and all the branches of snakes are too similar to have evolved convergently, while hollow snake teeth probably evolved two or three separate times.

I don't believe there's a specific instinct that's tied to snakes in particular. We know that there are plenty of mammalian instincts around motion detection and responding to being startled, and to me it sounds way more likely that it's just those in effect in all these anecdotes. You also probably wouldn't remember all the snakes you never noticed so there's potential for some heavy confirmation bias.
I'd also claim that if there were an instinct about detecting snakes, babies should have it? They're probably the most food-sized a human can get (even if they're still too big for most snakes and humans in general are an awful shape for swallowing because of our broad shoulders) Well, apparently babies have no inherent response to snakes and any fear of them is probably learned. Here's a video: https://youtu.be/3L4lxusff1c

But, if we're doing ancdotal evidence my own evidence is that I was reading emails with my snake on my lap the other day and didn't notice her scooting away into my chair until it was already too late and she was firmly wedged in there. Had to poke her butt to coax her into coming out from there.

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