with t1 as (select 'DUMMY' X from dual) 
select t2.*
  from bibtest t1,
       bibtest_2 t2 
 where t1.a = t2.a;

When writing a query, you can use aliases that match the names of other schema objects:

create table t as 
  select level c1 from dual
  connect by level <= 5;
  
create or replace view vw as 
  select count(*) c from t;
  
select vw.* from t vw;

C1   
    1 
    2 
    3 
    4 
    5 

select * from vw;

C   
   5 

In the first query above, the table alias matches the name of the view we created. The database resolves this to the table because the view isn't referenced in a from clause. Thus it's out-of-scope.

Think of the with clause as defining an on-the-fly view. So even though a table alias matches the named subquery, you've not accessed the CTE in the query itself. Thus the query never references the CTE's contents.

For example, the query below uses a with clause having the same name as a table alias, but the main query doesn't select from the CTE. So just like any other view in the schema, the database ignores its contents and dual is not read by the query:

set serveroutput off

with t1 as (
  select dummy from dual
)
  select * from t t1;
  
C1   
    1 
    2 
    3 
    4 
    5 
  
select * 
from   dbms_xplan.display_cursor( format => 'BASIC LAST' );

----------------------------------                              
| Id  | Operation         | Name |                              
----------------------------------                              
|   0 | SELECT STATEMENT  |      |                              
|   1 |  TABLE ACCESS FULL| T    |                              
----------------------------------

If you do access the CTE, the database is no longer able to resolve the query and throws an error:

with t1 as (
  select dummy from dual
)
  select * from t t1, t1;
  
ORA-00918: column ambiguously defined