Yeah, it was unexpected for me too. But the application's UI was changed right after the release candidate 1 issued.
Update is compatible with v21.0.1, so you can safely overwrite your Phos Light theme files right now.
Fixed:
- Color background for error message under the Settings>Audio removed.
Improved:
- Resolution of the icons increased for the standalone dialog messages (scaled up UI improvements)
Some other minor changes.