The point is that you can use a different device as the thread border router, it doesn’t have to be the SmartThings hub. So you can use a V2 hub and add thread devices to your SmartThings account as long as you have yet another device to act as the thread border router. This is often a smart speaker because a number of the models from different brands now have a TBR built-in.
this is all covered in both the community FAQ and the official FAQ on Matter.
FAQ: What do I need to add a Matter device to the SmartThings app? Do I need a bridge router device?