Uh, they did test the X1900XT 256MB (against the 7950GX2, 7900GTX and X1950XTX)
The only real card that is missing is X1950 Pro, but that is excusable because the review must have been coming for a little time. They probably didn't get any samples (though they could've got an X1900GT which would probably return close to identical scores).
I'm assuming drivers were all set to default like most websites do.