I certainly think so.
For example, if a group of singers were to learn a chant from the same recording, and each individually attempt to follow the nuances precisely (speed up here; barely lengthen this note,) and/or if the group spends time rehearsing together and agreeing upon rhythms and flow, then is a director really necessary?
I have found myself in the position of being "director," and yet, once I feel like I've "taught" the group, either by example or explanation of specific phrases, I can't help but wondering if all of my arm-waving is superfluous. Perhaps even moreso with some very amateur groups: if they have learned the chant more by ear than reading the notes-- wouldn't they be less affected by small nuances in conducting?
On the other hand, I have found myself in a situation of singing chant in a group with advanced singers and a superb conductor, and after extensive rehearsing, I feel as though I am so familiar with the director's every move, that we are already doing what he is directing, and if he stopped conducting, we would sound the exact same.
Perhaps I am not such a good chant singer or director, that I am not aware of the extent of the affect that conducting can have?