Datetime input-parsing shortcoming

Seen with current sources and with 6.4.2:

When datestyle = 'Postgres,European', the datetime parser will accept
dates written in either US or Euro order:

regression=> set datestyle = 'Postgres,European';
SET VARIABLE
regression=> select 'Wed 06 Jan 16:10:00 1999 EST'::datetime;
?column?
----------------------------
Wed 06 Jan 16:10:00 1999 EST
(1 row)

regression=> select 'Wed Jan 06 16:10:00 1999 EST'::datetime;
?column?
----------------------------
Wed 06 Jan 16:10:00 1999 EST
(1 row)

But when datestyle = 'Postgres,US' it won't:

regression=> set datestyle = 'Postgres,US';
SET VARIABLE
regression=> select 'Wed Jan 06 16:10:00 1999 EST'::datetime;
?column?
----------------------------
Wed Jan 06 16:10:00 1999 EST
(1 row)
regression=> select 'Wed 06 Jan 16:10:00 1999 EST'::datetime;
ERROR: Bad datetime external representation 'Wed 06 Jan 16:10:00 1999 EST'

A bug, no??

regards, tom lane