You keep assuming I am running something like SNTP.
I am not.
The system runs NTP and has an attached USB GNSS receiver that keeps the system to within about 3 milliseconds absent any other time source, but it also uses two local stratum 1 NTP servers that keep the system to well within 100 microseconds when it is on the network, which is most of the time. The system clock does NOT drift outside the microsecond range.
Perhaps if I rephrase the question: Would it have much effect on the resources used if the documentation suggestion to run something like NTP was changed to a requirement to keep the clock within, say 100 milliseconds or so?