When you run a Google Web search, Google's algorithms try to look for your search keywords in several places including Web page titles, text, and URLs.
If you want, you can use Google's Advanced Search filters to narrow down your search to specific areas.
This trivial to small-sized bug occurs when you try to search only in Web page body text: Advanced Search Page -> Where your keywords show up -> In the text of the page.
The problem is the Web body text searches incorrectly use the search operator as a literal search keyword instead of as an operator. You can easily see the bug if you try any of these searches: