Everything is an arrangement. It is impossible to perform a song without some sort of arrangement or other--"12 people singing the unadorned melody" is a different arrangement than" 9 people singing the unadorned melody"--especially since, try as one might, it is impossible to get nine people to sing anything exactly the same--and different tempo, different dynamics, and, particularly will unaccompanied singing, different absolute pitch.

As for myself, I would be hard pressed to find a reason to record the same arrangement of a song that someone else did--especially if it was folk music--what's the point in it?