The reduced range affects frag grenades but smoke grenades are affected far less because they do not have to land on the HMG to be effective.
I would argue that the change has nerfed infantry using frag grenades but infantry using smoke grenades are nearly untouched.
They don't have to land on the HMG to have an effect, but landing a smoke grenade on the HMG is more effective than landing it some distance in front of it. The HMG does not have to fall back as much before being able to set up safely again and much less of its firing cone will be obscured.