In Hong Kong kale is very much a cabbage. I can't see much difference between it and flowering cabbage except for lack of flowers. That said, Hong Kong is notorious for its own "English" names for many veggies so it's not trustworthy
I even used yo think flowering cabbage and kale were two alternate names for one thing, until I saw them next to each other on the shelf.
I'll take photos of kale the next time I buy it and post them here.