That phrase was probably the pre-programmed command for the X to disappear. I haven't been in a modern control room but back in the day, computers weren't widespread in TV news. You could type the text into the CHYRON generator, make it any size you wanted and have it ready for when the director called for it. You would push the lever up and the text would appear onscreen for whatever purpose. I'm sure that with things being more controlled by computers, some doofus created the X and rather than tabbing down to type in his command, accidentally typed it on the screen portion and then re-typed it in the command space, not realizing that he previously typed into the screen. Sort of like when using Yahoo mail, the cursor jumps back into the address field, after you thought you tabbed into the text field. Just my theory.
"You could type the text into the CHYRON generator, make it any size you wanted and have it ready for when the director called for it."
They still use Chyron CG's but they've been computer automated for over 10 years. I know first hand, because 10 years ago I wrote software to design screens and automate them via serial port. My handiwork was on air for the '96 election, and for all I know, the code is still in use. Maybe it's my fault! :)