Apple today released a macOS Big Sur 11.6.1 beta for developers to test purposes. The update comes two weeks after macOS Big Sur 11.6 was launched.
Registered developers can download betas through the Apple Developer Center. Once the profile has been installed, betas are available via the Software Update mechanism within System Preferences.
Apple released notes stating that the update "improves macOS security." Although it is not known why the beta version is being released to only beta users, there is a developer beta available for macOS Catalina.