Yes, this type of registration is known as a "standard character mark" and is very common, especially for clothing brands and marks used on clothing.
Some words or phrases are considered generic enough where they are unable to be registered.
But when a word or phrase becomes part of a brand or pop culture phenomenon, then it ceases to be generic and potentially becomes the intellectual property of the rightful owner.
As mentioned, marks can be registered as standard characters. And it seems that many of Summit Entertainment's Twilight-related submissions are "standard character marks" and a few are stylized designs.
Either way, it's obvious that they are looking to protect as much of their material as they can.
The best rule of thumb is "if you didn't create it, someone else did." So when attempting to put a title, phrase or character on a shirt and you know you didn't create the title, phrase or character, then you should know there is some element of risk.
I understand what you're saying about the word itself being too vague. But obviously, it ceases being vague when it's the title of a huge movie. That doesn't automatically make it infringement to use, but ignoring the risks would be foolish.