PurgeCSS analyzes your content and your css files. Then it matches the selectors used in your files with the one in your content files. It removes unused selectors from your css, resulting in smaller css files.
Current size on master: dist/css/data-bridge.app.css 31.52 KiB gzipped: 4.57 KiB
Size on the related patch: dist/css/data-bridge.app.css 21.88 KiB gzipped: 3.88 KiB
The radio button style looks different from production. My suspicion is something getting purged from normalize.css