Hibernate insert fails - java.sql.SQLException: Invalid arguments in call

I'm trying to insert the user object to Oracle with Hibernate. Object is loaded with values entered in the user registration form.

id is @GeneratedValue
pass is @Transient

These are the properties of User and UserType classes:

@Entity
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(length = 50, nullable = false)
    @NotBlank(message = "Boş bırakılamaz.")
    @Size(min=2, max = 50)
    private String firstName;

    @Column(length = 50, nullable = false)
    @NotBlank(message = "Boş bırakılamaz.")
    @Size(min=2, max = 50)
    private String lastName;

    @Column(length = 50, nullable = false)
    @NotBlank(message = "Boş bırakılamaz.")
    @Size(min=2, max = 50)
    private String userName;

    @Column(columnDefinition = "char(128)")
    private String passHash;

    @Column(columnDefinition = "char(32)")
    private String salt;

    @ManyToOne
    @NotNull(message = "Boş bırakılamaz.")
    private UserType userType;

    @Transient
    @NotBlank(message = "Boş bırakılamaz.")
    @Size(min=4)
    private String pass;
}
@Entity
public class UserType {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(length = 50, nullable = false)
    @NotBlank(message = "Boş bırakılamaz.")
    private String name;
}

This is the Oracle DDL:

create table DH_USER
(
    ID          NUMBER(19) generated as identity
        primary key,
    FIRSTNAME   VARCHAR2(50 char) not null,
    LASTNAME    VARCHAR2(50 char) not null,
    PASSHASH    CHAR(128),
    SALT        CHAR(32),
    USERNAME    VARCHAR2(50 char) not null,
    USERTYPE_ID NUMBER(19)        not null
        constraint FKO3DS41MXQLO527MM8H8J7F0FL
            references DH_USERTYPE
)
create table DH_USERTYPE
(
    ID   NUMBER(19) generated as identity
        primary key,
    NAME VARCHAR2(50 char) not null
)

After adding logging.level.org.hibernate.SQL=DEBUG and logging.level.org.hibernate.type=TRACE to application.properties file, critical part of the log is now like this:

2020-12-08 15:41:59.256  INFO 6676 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet        : Completed initialization in 1 ms
2020-12-08 15:41:59.356 DEBUG 6676 --- [nio-8080-exec-2] org.hibernate.SQL                        : select usertype0_.id as id1_1_0_, usertype0_.name as name2_1_0_ from DH_UserType usertype0_ where usertype0_.id=?
Hibernate: select usertype0_.id as id1_1_0_, usertype0_.name as name2_1_0_ from DH_UserType usertype0_ where usertype0_.id=?
2020-12-08 15:41:59.379 TRACE 6676 --- [nio-8080-exec-2] o.h.type.descriptor.sql.BasicBinder      : binding parameter [1] as [BIGINT] - [2]
2020-12-08 15:41:59.481 TRACE 6676 --- [nio-8080-exec-2] o.h.type.descriptor.sql.BasicExtractor   : extracted value ([name2_1_0_] : [VARCHAR]) - [Yönetici]
2020-12-08 15:41:59.830 DEBUG 6676 --- [nio-8080-exec-2] org.hibernate.SQL                        : insert into DH_User (id, firstName, lastName, passHash, salt, userName, userType_id) values (default, ?, ?, ?, ?, ?, ?)
Hibernate: insert into DH_User (id, firstName, lastName, passHash, salt, userName, userType_id) values (default, ?, ?, ?, ?, ?, ?)
2020-12-08 15:41:59.834  WARN 6676 --- [nio-8080-exec-2] o.h.engine.jdbc.spi.SqlExceptionHelper   : SQL Error: 17068, SQLState: 99999
2020-12-08 15:41:59.834 ERROR 6676 --- [nio-8080-exec-2] o.h.engine.jdbc.spi.SqlExceptionHelper   : Invalid arguments in call
2020-12-08 15:41:59.863 ERROR 6676 --- [nio-8080-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.orm.jpa.JpaSystemException: could not prepare statement; nested exception is org.hibernate.exception.GenericJDBCException: could not prepare statement] with root cause

Why does Hibernate add the id field into the insert statement?
id field is "generated as identity" so doesn't need to be involved in the query.
And why does it try to insert "default" into id column? It should use null instead of default, as null is the value of user.id at that point in the code.

DH_User (id, firstName, lastName, passHash, salt, userName, userType_id) values (default, ?, ?, ?, ?, ?, ?)