Interesting! Anybody got a pic? Not stock vendor pics, but something from a tank? I've got a small carpet that started out as 1" bunches. I didn't have the patience to go one or 3-4 stems at a time, but I've been tempted to find my inner peace sometime and plant a single stem at a time. It would be the fastest way to grow a carpet, but the time and patience required would be a tall order. If you can pull it off, go for it? If not, the smaller the clump, the better.
P.S. I've found that when in groups, making a shallow depression, placing the clump in it, and then sprinkling with substrate is pretty efficient.