F-Droid Build Status was updated to 5.6.4 and no one will get this update. Why? Well, the app is now built reproducibly so if you have it installed you need to uninstall it and then reinstall it. (Yes, we wish this switch to be easier to perform, but the UI is not there yet)
This part of your comment is not quite true. One of the advantages of reproducible builds is that the app can be signed by the developer but fdroid can still verify that it has been built from the correct source code. You can check out the documentation here: https://f-droid.org/docs/Reproducible_Builds/
you’re right, thanks for letting me know
then I don’t understand it either why it can’t be updated directly
Because there will be a signature mismatch. Apps built by F-Droid will use the F-Droid signature, reproducible apps will use the dev signature.
If an app doesn’t support reproducible builds, the version you can download from F-Droid was built and signed by F-Droid, not by the dev