Folks,
We have released a blog about the mappings of GeoDNS, how it gets to choose who sees which servers:
https://www.sidnlabs.nl/en/news-and-blogs/ntp-pool-the-internet-timekeeper
It’ s based on a paper that we have also published:
Deep Dive into NTP Pool's Popularity and Mapping | Proceedings of the ACM on Measurement and Analysis of Computing Systems (open access)