Oracle 23 introduced the ability to specify a SELECT statement without a FROM clause, see the grammar differences here:

21 -> https://docs.oracle.com/en/database/oracle/oracle-database/21/sqlrf/SELECT.html#GUID-CFA006CA-6FF1-4972-821E-6996142A51C6__CHDDCHGF
23 -> https://docs.oracle.com/en/database/oracle/oracle-database/23/sqlrf/SELECT.html#GUID-CFA006CA-6FF1-4972-821E-6996142A51C6__CHDDCHGF