Microsoft is the one that determines which Processor is compatible with Windows 11.
So far all 1st generation Ryzen processor (1000 series ) are not compatible. Only 2nd Generation (2000 series) and newer AMD processors are compatible.
You will need to wait until Windows 11 is officially released to the public to see if any 1st generation processor has been added to the CPU COMPATIBILITY LIST for Windows 11 or not.
Windows 11 is being tested with various processors not included in Microsoft processor compatibility list before being officially released. If those Users testing non-compatible processors shows it is compatible then it will be added to Microsoft Compatibility list for Windows 11.
Basically I believe the reason why the 1st generation processors are not included it doesn't have the security or technical features of the 2nd generation processors and above. just my opinion.