Can muscle attachment surgery in the upper lip make a difference in functionality and appearance?

Yes, missing or underdeveloped muscle in the upper lip can absolutely affect both the appearance and functionality of the lip.
Flattening or asymmetry of the upper lip
Reduced volume or definition.
Visible imbalance when smiling or at rest
Irregular contour that may look like a “dent” or hollow area
Puckering the lips
Difficulty puckering or forming a tight lip seal
Slight speech articulation issues

And that is because of:
Congenital muscle hypoplasia (underdevelopment present from birth)
Cleft lip repair history (muscle may not be fully reconnected or reconstructed)