If they're really tracking the same 100 identified people, with no replacement, then you'd expect the same result even without regression to the mean, simply be

If they're really tracking the same 100 identified people, with no replacement, then you'd expect the same result even without regression to the mean, simply because very sick people tend to die, and dead people tend not to call 911. One would hope that they're not doing that, and it's just that the article is imperfectly worded.