Not so much, Marlene used to always fill in for Flo at times. I think the Andantes added additional background vocals to "Stop! In the Name of Love" too. Matter of fact, when I heard it on my #1's CD, I thought I was hearing the Andantes than Mary and Flo. But they could've all been on it.
Try it, you'll like it/what the world needs now/is a little more love... - Marvin Gaye