Versions of SQL listed in Premium SPM specifications

The current SPM for v2020 (and v2021) both list compatibility with SQL 2017 CU "20 and earlier"...

...yet the current CU# is 23. 

https://docs.microsoft.com/en-us/troubleshoot/sql/general/determine-version-edition-update-level

Is there a compatibility problem with the latest SQL CU?  Or can the SPM be updated?