As a follow-up, if you use the Quick DDL option for an object (and you have the option to include grants setup in Tools>>Preferences, then Database>>Utilities>>Export), the Grants display properly.
Using version 22.214.171.124 (Build 15.21) here. I log in with my own account, which has SELECT_CATALOG_ROLE, then try to use the Grants tab for objects owned by another user. I've noticed (by peeking into V$SQL) that the Grants tab for tables uses the DBA_COL_PRIVS and DBA_TAB_PRIVS views, but the Grants tab for PL/SQL uses ALL_COL_PRIVS and ALL_TAB_PRIVS. This would explain the missing privileges I've seen so far.
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