You are absolutely correct... If you look at the photo posted 3/25/06, you can see how this usually looks. The plant I have in there is somewhat similar to HM, I call it "Two-leaved Pearlweed". Regular Pearlweed has 3 or more leaves around each node.
So anyway, there are 4 stages of this plant:
1. Little stems stuck in substrate, like in that most recent picture.
2. As they grow in, shoots grow horizontally along the substrate. The long stems can be cut back.
3. This is the good-looking phase... nice dense substrate-hugging lawn.
4. Overgrowing phase... cutting back is hopeless and frustrating due to the density of the plant, and the thousands of little pieces floating through the tank. So, pull it all out, and start over at phase 1.
Unfortunately, it is a pretty fast growing plant, so these phases are not very long. Here is a picture from a different tank where you can see stages 2 through 4...