Hibernate with Oracle-Dialect only validates against Sequences of the currently logged in DB-User since 5.4.13. This is because this change, which only looks for user_sequences (before: all_sequences). .
But a very typical Setup is to use a DB-Run-User (without DDL Rights) and fully qualify sequences with the owner-schema, for example MYOWNER.MY_SEQUENCE. This does NOT work with Hibernate 5.4.13.Final and above anymore (Schema-Validation Error).