confused by int2vector typdelim

hi.
select
pt.typtype
, pt.typcategory
, pt.typdelim
, pt.typelem
, pt1.typname as elem_type
,pt.typsubscript
,pt.typname
from pg_type pt join pg_type pt1 on pt.typelem = pt1.oid
where pt.typname = 'int2vector';

returns
typtype | typcategory | typdelim | typelem | elem_type | typsubscript
| typname
---------+-------------+---------+----------+-----------+-------------------------+------------
b | A | , | 21 | int2 |
array_subscript_handler | int2vector
(1 row)

from manual:

> typdelim char
> Character that separates two values of this type when parsing array input.
> Note that the delimiter is associated with the array element data type, not
> the array data type.

should I expect the typdelim be a white space? Since '1 2'::int2vector
works, '1,2'::int2vector does not work.