Giovane, thanks for sharing this. Interesting material and concerning to see that MacOS and Windows are so vulnerable…
The reference section als contained some interesting references to earlier studies.
Especially the Deep Dive on the NTP Pool! This might add some valuable insight about underserved zones.
Especially one of the assumptions by pool operators about helping underserved zones by other (more distant pool servers) is addressed. This assumption is that because of physical distance between a pool server and client(zone) it makes no sense to add pool servers from zones not physically adjacent to the clientzone. The conclusions of this deep dive support the idea that it might make sense to add servers from a more distant zone while still providing a solid NTP service.