Sorry about your one more hurdle CPAP addition. I too was put on CPAP before surgery. I was one point (5.9 so 6) above the not needing it - it sucks I know. Just tell yourself.. Just one more step closer to your surgery.
What's odd is my CPAP score has gotten a lot worse since I had surgery! I was told (IF you can talk to a sleep doctor), they tend to diagnose / prescribe then from then on its crickets telling you its now under your GP's care - except they're not specialized in reading CPAP scores or diagnosing the machines data - that the change is due to my weight loss due to mask leaks...right...I have the nasal mask and its not influenced by weight gain/loss, so I've quit using it for now, especially since I'm past the required 3 months of usage by the insurance company.
So again, just do what you have to by jumping through their hoops to become healthier and get your surgery!