wordpress. Why is the 404 status buggy when the CNC is on?

Question

Apache HTTP Server

The problem is this: If you enable CNC in WordPress and add recommended rules to .htaccess, then Google crawler stops understanding 404 errors, and sees 404 pages with status 200, if you remove all rules from .htaccess, then everything is OK, 404 works fine. What are the options for solving the problem?
.htaccess file content:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

Answer 1

There is no such problem in WP. This behavior can be changed by the theme or plugins. Deal with them.

Answer 2

Do you go to mysite.com/404.html and see an error page?
That's the way it should be. This is the html file, and it is. And why fix it?