permissions – Oracle allows inserting into table even after revoking quota

I am studying creating users and granting roles and I have come across this scenario where I grant unlimited quota to a user, insert into the table and then revoke the quota. I expected that after setting quota to 0, the user would not be able to insert into the table. However, the user is still able to insert. I wonder if this is expected, if there is another command to really prevent the user from inserting again. I am using Oracle 19c and user’s current priviledges are create session and create table.

sqlplus systemoracle

SQL> CREATE TABLESPACE libgeneral datafile '/u01/app/oracle/oradata/ORCLCDB/orcl/libgeneral.dbf' SIZE 20M AUTOEXTEND ON NEXT 40M
EXTENT MANAGEMENT LOCAL
SEGMENT SPACE MANAGEMENT AUTO;

Tablespace created.

sqlplus librarylibuser

SQL> create table t1 ( idx number ) tablespace libgeneral;

Table created.

SQL> insert into t1 values (1);
insert into t1 values (1)
            *
ERROR at line 1:
ORA-01536: space quota exceeded for tablespace 'LIBGENERAL'

sqlplus systemoracle

SQL> alter user library quota unlimited on libgeneral;

User altered.

sqlplus librarylibuser

SQL> insert into t1 values (1);

1 row created.

sqlplus systemoracle

SQL> alter user library quota 0 on libgeneral;

User altered.

sqlplus librarylibuser

SQL> insert into t1 values (1);

1 row created.