I was browsing the "Consensus health" page and something let me curious... What is the importance of the clock skew in the authorities with the resolution of microseconds?

Also, how the authorities compare their clocks? Using ntp daemon for example? I'm asking this here because I work in a time and frequency reference lab and have two NTP (stratum 1, connected directly to UTC(LRTE) timescale. And a stratum 2 that is discilplinned with the stratum 1 timeserver). So considering the microssencond accuracy did the keepers of these authorities care about the time source? Or any time source is ok?