I don't believe this issue is specific to the bug fix in the latest Beta 2.3.0.2119:
In v1.10.6 and v2.1.1 it is possible to delete System Palettes from the Swatches Panel but In the current Beta, the option to Delete a System Palette is greyed out.
The only way to delete a System Palette in the current Beta is to delete it using v2.1.1 or v1.10.6.