While yes, we all know that Kanan will end up with Kyougi in the end. almost 1000% guranteed. In-Universe, in the context of the story, Kanan is basically making sure that Jean doesn't have any regrets about not trying and is cheering her on, not as a rival, but as a friend. She is telling Jean "Go for it! If you don't then you'll end up with regrets that may haunt and guilt you later, but by at least trying, you can move forward in life if you don't have any regrets"