Qualified Expressions Quite Puzzling - Part Three: Bug!

After some back and forth with Patrick Barel and Steven Feuerstein, it became clear that it most likely is a bug with Qualified Expressions.
A simple case to reproduce the bug is below

SQL> set serveroutput on


SQL> declare
  2     type tbl_t is table of pls_integer
  3        index by pls_integer;
  4     l_tbl tbl_t;
  5     l_idx pls_integer;
  6  begin
  7     for i in 1..3
  8     loop
  9        l_tbl := tbl_t (i => i);
 10     end loop;
 11     --
 12     l_idx := l_tbl.first;
 13     while l_idx is not null
 14     loop
 15        sys.dbms_output.put_line (to_char (l_idx)
 16                                 ||' - '||
 17                                 to_char (l_tbl(l_idx))
 18                                 );
 19        l_idx := l_tbl.next (l_idx);
 20     end loop;
 21  end;
 22  /


1 - 1
2 - 2
3 - 3


PL/SQL procedure successfully completed.

Why it is the above a bug? If you do the a similar assignment, but without a loop, the outcome is different (and most likely correct)

SQL> declare
  2     type tbl_t is table of pls_integer
  3        index by pls_integer;
  4     l_tbl tbl_t;
  5     l_idx pls_integer;
  6  begin
  7     l_tbl := tbl_t (1 => 1);
  8     l_tbl := tbl_t (2 => 2);
  9     l_tbl := tbl_t (3 => 3);
 10     --
 11     l_idx := l_tbl.first;
 12     while l_idx is not null
 13     loop
 14        sys.dbms_output.put_line (to_char (l_idx)
 15                                 ||' - '||
 16                                 to_char (l_tbl(l_idx))
 17                                 );
 18        l_idx := l_tbl.next (l_idx);
 19     end loop;
 20  end;
 21  /


3 - 3


PL/SQL procedure successfully completed.

Bug 32057533 - ASSIGNMENT TO COLLECTION USING QUALIFIED EXPRESSION APPENDS INSTEAD OF REPLACING.