Oracle Table Type Needs Multiple Rows

I have a type and a table of that type
type INV_TABLE is the table
type INV_TYPE is the type

Why cant I insert multiple rows into the table.
It only ever outputs one row with  select * from table(GET_INVENTORY(97));

create or replace
function get_inventory(in_var in number) return INV_TABLE is
      
   test_recs  INV_TABLE;
    
    begin
     
  SELECT  INV_TYPE( 1, 'A',  2,  'B' )
    BULK     COLLECT
    INTO     test_recs
    FROM    dual;
       
     --only this is seen with test:
    SELECT  INV_TYPE( 1, 'A',  2,  'C' )
    BULK     COLLECT
    INTO     test_recs
    FROM    dual;
    
-- insert into test_recs values( 1, 'A',  2, 'B' ); --does not work. why?
 
    RETURN test_recs; 
 
    end;

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