I know nothing about this variety but Baker Creek says that it is more closely related to bok choy than Chinese cabbage. It looks like a very large, white-stem bok choy.
The roots of the green-stem, small bok choy that I grow are not left in the ground after harvest. I have never felt the need to do that since our mid-Summer is not at all the season to expect much from the plants. There is quite a lot of ground allocated to bok choy early and then, since they usually follow an early harvest of potatoes, there is plenty later. They survive our Winters poorly, if at all.
The picture Baker Creek has shows such robust plants that I am thinking that it may be worth a try to see how well it can regrow. Tiara cabbage does very well with producing side buds somewhat like Brussel sprouts after a first harvest. It is known for that. but other cabbage varieties are not. On the other hand, if you have a fall planting of something else and limited space, you might not want to take the risk that it won't produce something worthwhile.
Steve
