Subselects open issue Nr. NEW

Hm, new one. Oracle 6:

SQL> select * from a where (x,z) in (select y, l from b);

         X          Z
---------- ----------
         1          2

SQL> select * from a where (x,z) = ANY (select y, l from b);

         X          Z
---------- ----------
         1          2

SQL> select * from a where (x,z) >= ANY (select y, l from b);
select * from a where (x,z) >= ANY (select y, l from b)
                            *
ERROR at line 1:
ORA-00920: invalid relational operator

: only '=' and '<>' are allowed if there are more than one 
expression on the left side of clause with subselect...

Is this in standard or Oracle' preference ?

Vadim
P.S. Maybe I should ask in DB newsgroups ?..