Good question, but when I went shopping last year I found most banks offered identical rates, but the difference were in the terms like how much you could make in extra payments per year
I am not sure I agree with a stress test exemption if you are renewing with the same bank (is this the only exemption after Jan 1?). It really gives carte blanche to the banks to say here is your renewal rate, take it or face a stress test at the other banks. I don't think we will know the rate difference until next year