If Javascript is disabled in the web browser, typing words into the wikipedia search box (under Vector) and pressing Enter does not take you directly to the page, even when an exact page title match exists. Instead, you go to a search results page.
Under Monobook, typing words and pressing Enter takes you directly to the matching page.
To get the Monobook behavior in Vector, you must enable Javascript in the web browser.
Looks like the decision to make Vector work like that was intentional: https://github.com/wikimedia/mediawiki-skins-Vector/blob/master/VectorTemplate.php#L558
Reopen. I propose to remove this behavior - if you try to enter something in the search bar and hit enter before JavaScript is fully loaded (even if JavaScript enabled), this bothers me multiple times. The fulltext search feature is still reachable by directly hitting enter before entering any term which will lead to a full text search page.