I'd actually argue that the security and web server architecture wouldn't be lumped to the role of a "full stack developer." That's more dev ops/system administrators roles, at least at my company. Actually, our lead developer fulfills all the things you wrote down and he also does a lot of the architectural work for new servers and routes.
If you define a stack as the technologies used in the development side -- and that's implied in my opinion -- the terminology isn't that farfetched.
I think you have a range of companies latching onto the terminology. However, in writing this I searched for job postings and articles on how to become a full stack developer and the skills needed, and I'd say that by and large the expectations for most of these were on the outlandish side as opposed to reasonable.
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