I find this approach bizarre and honestly kind of backwards. My favorite math professor assigned homework but essentially (sometimes literally) didn't grade it at all. It was strictly for our own learning. I did it on scratch paper and threw it away, but enjoyed it more because I didn't have to worry about formatting it for clarity. The exams constituted almost all of our grade, and were plenty to convince at least me to take the exercises seriously. I've often wished every mathish course was taught this way. You don't have any choice but to change the exams every time (or people will cheat), and exercises are entirely designed to help us learn, so why not lean into it?