Hmmm. Very interesting ... if true.
Seems unlikely. From investigating why my cabbage failed, I can tell you that kale, cauliflower, cabbage, Brussels sprouts, kohlrabi, and broccoli are all the same species of plant, Brassica oleracea, all descended from the wild cabbage of southern and western Europe. Its closest relatives, also in the genus Brassica, include wild and cultivated mustard plants, B. napus (the rutabaga), and B. rapa (the turnip). Trivia for the day :)