Had I been under the impression it was that easy, I would have attempted removing the grill on my 2018 Expedition to install the remote antenna for my radar detector, and to move it to my 2022 Expedition if I ever get it.
However the Ford service manual's (2018 & 2022) describe the process to be much more complicated then you describe. But I don't know for sure as I gave up on the idea, and just installed the antenna working through the small grill openings.
Apparently there are grill lower mounting screws covered by the bumper cover. So the next step after removing the upper air deflector is to remove the bumper cover, according to the manual, looks quite tedious. Many screws, clips/pins and an electrical harnesse.
Dennis