"I dug into the subject of polyphasic sleep and read a couple very personal accounts of people who made it work for them for extended periods (several months or more). I never tried it myself, but I don't believe they were any less "creative" or functional during this time, or that they were doing long-term damage."

Chronic sleep deprivation doesn't cause obvious, self-evident damage at the time, and it's not always obvious to the person who's experiencing it. But it can cause serious, serious problems over time. That is essentially the effect of sleep apnea. The effects are subtle enough that an enthusiastic confirmation-biased person would easily miss them over a period of "several months or more", but they're real and they get worse over time.