I had the same thought. Does the world really need another (presumably) stratum-3 server running in Amazon's cluster, when Amazon already runs a pool of stratum-2 servers? ([0-3].amazon.pool.ntp.org).
By my recent reading of the AWS docs, those pool addresses are not run by Amazon. They are DNS names that allow NTP load from AWS to the NTP pool to be distributed more fairly.
Ok, interesting.
It's a vendor zone, anyone can register for a vendor zone...