clob变量值无法使用v$sql_bind_capture获得

clob情况：
SQL> variable test_c clob;
SQL> exec :test_c := 'test';

PL/SQL procedure successfully completed.

SQL> select * from test_clob where dbms_lob.substr(name,4000)=dbms_lob.substr(:test_c,4000);

NAME
--------------------------------------------------------------------------------
test

SQL> select sql_id,sql_text from v$sql where sql_text like 'select * from test_clob%';
65v08jhcjtuun
select * from test_clob where dbms_lob.substr(name,4000)=dbms_lob.substr(:test_c
,4000)


SQL> select value_string from v$sql_bind_capture where sql_id='65v08jhcjtuun';

VALUE_STRING