only add his would-be wife name in the 485 form follow to join?

my friend discuss one issue with me :

his girlfriend current visa is F1 ,they are not marry yet, the girl told him she will marry him at later time, not sure ,
now this guy hold H1 visa , will apply NIW soon . the first step file I140 , as no marry, no add his girlfriend( later on become " wife " ) name , so he will add her name in the I485 form as " follow-in join," provided his 140 approved.

this approach is okay?