[Bug]: exclude broken for md files about jekyll HOT 3 CLOSED

$ jekyll --version
jekyll 4.3.3

$ jekyll new test-exclude-md
Running bundle install in /home/mkasberg/code/test-exclude-md... 
New jekyll site installed in /home/mkasberg/code/test-exclude-md. 

$ cd test-exclude-md 

$ echo "testing" > README.md

$ bundle exec jekyll build
Configuration file: /home/mkasberg/code/test-exclude-md/_config.yml
            Source: /home/mkasberg/code/test-exclude-md
       Destination: /home/mkasberg/code/test-exclude-md/_site
 Incremental build: disabled. Enable with --incremental
      Generating... 
       Jekyll Feed: Generating feed for posts
                    done in 0.374 seconds.
 Auto-regeneration: disabled. Use --watch to enable.

$ ls _site # NOTE README.md gets created because it's not yet excluded.
404.html  about  assets  feed.xml  index.html  jekyll  README.md

$ echo "exclude:
dquote>   - README.md" > _config.yml 

$ tail -n4 _config.yml 
exclude:
  - README.md

$ bundle exec jekyll build
Configuration file: /home/mkasberg/code/test-exclude-md/_config.yml
            Source: /home/mkasberg/code/test-exclude-md
       Destination: /home/mkasberg/code/test-exclude-md/_site
 Incremental build: disabled. Enable with --incremental
      Generating... 
       Jekyll Feed: Generating feed for posts
     Build Warning: Layout 'post' requested in _posts/2024-05-23-welcome-to-jekyll.markdown does not exist.
     Build Warning: Layout 'default' requested in 404.html does not exist.
     Build Warning: Layout 'page' requested in about.markdown does not exist.
     Build Warning: Layout 'home' requested in index.markdown does not exist.
                    done in 0.327 seconds.
 Auto-regeneration: disabled. Use --watch to enable.

$ ls _site # NOTE exclude works correctly and removes README.md.
404.html  about  feed.xml  index.html  jekyll