I'm confused by your use of "Keyword" and "Title." Which do you mean?
Here's the info window for a picture taken with a tour guide named "Hunter," and a woman named "Katy."

The Title says this is a Plantation. The Caption includes the name Hunter. I've added a Keyword, "Katy." And there's a face ID of "Katy."
If I use the search field to find "Hunter," then I get this picture and a couple of others with "Hunter" in them. I also get a picture of Orion. "Hunter" was not a keyword or in the Title-- it was in the Caption.
If I search for Plantation, I get this picture and a bunch of others taken at antebellum homes, because "plantation" was in the Title.
If I search for "Katy", I get pictures of "Katy," if "Katy" was a keyword or in the Caption, or had a Face ID.
The best way to search is to use a Smart Folder like this:

Then I get only 4 pictures: 3 with Hunter the guide, and 1 with Orion the Hunter.
I can use a Smart Folder to search for Bobcats,

and, because I entered the word "Bobcat" into the keyword field in pictures that have bobcats on my front porch or in the wild, I get pictures with bobcats in it. But if I hadn't entered the keyword bobcat into a picture with a bobcat, then I wouldn't get that picture.
With that, can you better explain what you're expecting?