Something similar yes, but much more complicated. With the index table engine it is completely different, it does not query the posts table at all, but a custom generated table with keyword occurences.
I created a test search, and enabled the search in the post contents only, and the result was found. Then I switched to search in titles only, to make sure it works correctly, and then the result was not found anymore.That means, the keyword is within the post content field for sure.
You can try looking up the posts database table directly, to see where exactly that keyword is printed. Maybe it is used in some sort of a data structure, which is later processed or removed in the front-end view. However it is definitely there in the database, otherwise it would not match.