Where are these reports of people being rested on polyphasic sleep? Can you post them? The site you linked suggests they still end up causing ill effects. Besides that, the extreme polyphasic schedules seem very inconvenient unless you stay home all day and strictly adhere to the schedule.
You are likely right about glycine and magnesium helping, but in most contexts I've seen people discuss them they still sleep the typical 8-9 hours
Ultimately, what I am seeking here is complete freedom from sleep cycles. The ability to stay awake or rest deeply as one desires, whenever one can or wants to.