The app description explains it:

The Basic version of F-Droid Client has a reduced feature set (e.g. no nearby share and no panic feature). It targets Android 13 and can do unattended updates without privileged extension or root.

It's a more minimal app with less features. It's released on there first so they can ask for feedback while maintaining all the existing functionality on the full app.

• https://f-droid.org/en/packages/org.fdroid.basic/
• https://f-droid.org/en/packages/org.fdroid.fdroid/

I see where this comes from, but it's funny because F-Droid is the very last place where I expect this to happen. Right after hell freezes over. Imagine them listing their own app with an anti-feature from their list: https://f-droid.org/docs/Anti-Features/