The root systems of Thyme and Oregano are fine and full. You can't possibly separate the plants into plant and roots without tearing them. Tomatoes for instance can be separated pretty easily. If you have 3 tomatoes in a cell, you can gently bang the root-ball and pull the plant and roots apart without much root damage.
But tomatoes are easily harmed if you just tore the root-ball apart. Thyme and Oregano can be grasped and torn when you practice the over planting method. Water and light will keep them going.
Here are what the root-balls look like fresh out of a cell.
|Oregan (L) and Thyme (R) Roots: Gary Pilarchik|
|Chive Roots: Gary Pilarchik|
|Chive Roots Close Up: Gary Pilarchik|