Steps to reproduce the issue

1. Install fresh Joomla 3.9.x
2. Create 4 Articles containing the following content:

• Article 1: article, sea, water, longboat, sunshine
• Article 2: article, wave, boat, beach, sunglass
• Article 3: article, sand, sun, iceboating, sailing
• Article 4: article, sandstone, sunburned, desert, camel

3. Activate "Content - Smart Search" plugin
4. Index content (Backend - Components - Smart Search - Index)
5. Create frontend menu item type "Smart Search - Search"
6. Switch to frontend and go to the page of your created menu item
7. Search with the search term "boat"

Expected result

Article 1, Article 2 and Article 3 showing up in the search results

Actual result

Only Article 2 showing up in the search results

System information (as much as possible)

XAMPP for Windows 7.2.28
Database Type MariaDB
Database Version 10.4.11-MariaDB
Database Collation utf8_general_ci
Webserver Apache/2.4.41 (Win64) OpenSSL/1.1.1c PHP/7.4.9
Joomla! Version Joomla! 3.9.24

Additional comments

With the com_search component i am able to generate the expected result. Com_search finds the three articles (Article 1, Article 2 and Article 3) as expectet.
In my understanding, the com_finder is the more advanced search and should deliver at least as good results as the com_search.