Why would mortgage rates go up if interest rates go down? What reasons or scenarios could cause a case where mortgage rates would rise if interest rates(federal funds rate) fall? Is that even possible?
Your ceteris paribus logic is correct however that not how the real world works.
And yes this happened in Canada spring 2020, It's because risk premiums went up. We could imagine that if the bank had inflation expectations they would want a real ROI &gt; 0 and thus those could move in opposite directions