The Google app obviously only searches Google, to search everything on your phone you have to search from the app launcher. There are even preferences of what to search, including contacts
Searches from app launchers are pretty limited too. Contact was just an example
Have you used Android a decade ago?
The search app was pretty comprehensive, it allowed you to include all Content Providers on the phone and search them.
For example, circa 2010, I wrote a Sign language app that included a Content Providers, if you typed a word in the search app, results from my app would be returned (along other content).
And I wasn't talking only about the Google app, all search app only display Web results, there's no app anymore to search the entire devicen: files, contact, messages, dictionnaries, music or whatever