What, that it's valid? Since it passes a syntax check it's valid T-SQL, hard to argue that it's not valid (unless in SQL 2012 that aliasing form has been removed and a query using that aliasing form fails a syntax check).

I never claimed it's a good idea or that it would magically prevent column order mistake, personally I don't like that form of aliasing and never use it. All I said was that it's a valid (ie correct, parsable) form of T-SQL.