Accurate timekeeping is critical infrastructure. So much so, that the US government operates many radio stations whose sole purpose is to provide current time announcements, reference clocks, and other timekeeping-related information. See [0].

Relatedly: surely you're not of the opinion that the various GPS constellations are not critical infrastructure?

[0] <https://www.nist.gov/pml/time-and-frequency-division/time-se...>

Just because other timekeeping projects are critical infrastructure doesn't mean that one NTP client is critical infrastructure.

Sure. I agree with you. You're absolutely correct.