I didn't say someone is accidentally going to end up at the wrong destination to see Scarecrow. (Not that that would necessarily matter, since it'll be at both...)
I'm pointing out that any announcements about Scarecrow in Hollywood and articles about Horror Unleashed (which will naturally prominently feature Scarecrow) are inevitably going to compete with each other if you're basically anywhere other than Los Angeles or Las Vegas. Search engine geotargeting tends to not be as precise or smart as I think you're suggesting unless you explicitly use geotargeted keywords (i.e. Halloween Horror Nights Hollywood).
Horror Unleashed doesn't even have Vegas as part of its official name. They do appear to be realizing the issue here, as I just checked -- the meta title now refers to the destination as "Universal Horror Unleashed in Las Vegas."
A simple fix here, as
@Jake S alluded to, would be to give either version of Scarecrow a different subtitle. Maybe Hollywood will get a different subtitle, which would help alleviate some (though not all) concerns.
Disclosure: I work in SEO.