Yes, but if You have geometry from step file, You don't have history. You can always extract this face / surface if You need it. You can also try delete face or replace face.
Right now I don't have a possibility to check NX 12, but if they removing this function - join face, it will be a pity. I often use it to join imported step files, because NX has a huge problem with this half circle, when You create drawing and try to place section on it. You receive an error.
With best regards
Michael