Based on your other post, it sounds like you are doing NTP with your ISP and then using PTP to sync your servers on the local network. Nothing about this implies that you are accurate to the global clock within a microsecond, let alone accurate within any number of nanoseconds.

With a correctly equipped and configured PTP installation locally, you can expect your clocks to be synchronized on the order of a very small number of microseconds with respect to each other, but the relationship between those and the atomic global clock is something else.

If you are using satellite/GPS time sources, then that's another matter. Why then is it relevant to have an NTP hookup at your ISP?

With A ISP, not my ISP. Also, I’m syncing with a Stratum 0 servers which are connected to an atomic clock and several GPS clocks.

Also, consistency and accuracy are orthogonal to each other. My servers clocks are consistent and fairly accurate in regards to global time.

Ah yes, I figured as much, this is why I skipped over the GPS and satellite parts initially. Having a high quality highly local NTP source is better than most sources, but it is nowhere near as close as having your own local time sources, which is what a lot of time sensitive installations do.

no-propagate-ttl really does clean up an ISP network.