I did a bit more digging on the FAA's diagnosis criteria. 5 AHIs per hour. That's considered mild apnea, but yes, it's likely that a very high percentage of pilots will be 'diagnosed' with OSA.

The science behind OSA is shaky at best; most reports you read will admit something along the lines of 'we can't prove anything, but we think it's a terrible affliction' or similar verbiage. This is simply a moneymaker for 'medical' vultures.