Oracle 10g small Blob or Clob not being stored inline?

According to the documents I've read, the default storage for a CLOB or BLOB is inline, which means that if it is less than approx 4k in size then it will be held in the table.

But when I test this on a dummy table in Oracle (10.2.0.1.0) the performance and response from Oracle Monitor (by Allround Automations) suggest that it is being held outwith the table.

Here's my test scenario ...

create table clobtest ( x int primary key, y clob, z varchar(100) )  
;
insert into clobtest 
   select object_id, object_name, object_name  
   from all_objects where rownum < 10001  
;
select COLUMN_NAME, IN_ROW 
from user_lobs 
where table_name = 'CLOBTEST'  
;

This shows: Y YES (suggesting that Oracle will store the clob in the row)

select x, y from CLOBTEST where ROWNUM < 1001 -- 8.49 seconds  
select x, z from CLOBTEST where ROWNUM < 1001 -- 0.298 seconds  

So in this case, the CLOB values will have a maximum length of 30 characters, so should always be inline. If I run Oracle Monitor, it shows a LOB.Length followed by a LOB.Read() for each row returned, again suggesting that the clob values are held outwith the table.

I also tried creating the table like this

create table clobtest 
    ( x int primary key, y clob, z varchar(100) ) 
    LOB (y) STORE AS     (ENABLE STORAGE IN ROW)  

but got exactly the same results.

Does anyone have any suggestions how I can force (persuade, encourage) Oracle to store the clob value in-line in the table? (I'm hoping to achieve similar response times to reading the varchar2 column z)

UPDATE: If I run this SQL

select COLUMN_NAME, IN_ROW, l.SEGMENT_NAME, SEGMENT_TYPE, BYTES, BLOCKS, EXTENTS 
from user_lobs l 
      JOIN USER_SEGMENTS s
       on (l.Segment_Name = s. segment_name )
where table_name = 'CLOBTEST'  

then I get the following results ..