When I was involved in the teaching of a course that allowed this, one student basically reduced all the course notes onto a single two-sided page, except they

When I was involved in the teaching of a course that allowed this, one student basically reduced all the course notes onto a single two-sided page, except they also had flaps on it to fit more in. The exam invigilator took it from them deeming it (correctly imo) to not be in the spirit of the allowance. We decided we'd mark their exam, and then determine what we should do about this cheating-cheat-sheet. Given they got something like 5% in the exam anyway, we decided to let it slide. My own experience of making up those cheat sheets is the same as yours, the effort put in to create them is an excellent teaching tool in itself, as you're studying and distilling all the stuff you don't know well, and by the time you're done, you hardly have to refer to it in the exam anyway. For physics, they'd just give us a page with all the formulas but with no context aside from the letters in them, so if you knew roughly what it should look like, you could find it and you're not at so much risk of making a basic error under pressure.