> This sounds like the "peer to peer" equivalent to PTP. It would require every node to maintain state about it's estimate (skew, slew, variance) of every other clock.

Well, it requires having the conversion function for each edge in the traversed path. And such function needs to exist only at the location(s) performing the conversion.

> obviously it adds complexity to end-stations beyond what PTP requires

If you have PTP and it works then stick with it. If you’re trying to timesync a network of wearable devices then you don’t have PTP stamping hardware.

> because packets traversing different routes

Fair callout. It’s probably a more useful model for less internty use cases. Of which there are many!

For example when trying to timesync a collection of different sensors on different devices/microcontrollers.

Roboticists like CanBus and Ethercat. But even that is kinda overkill imho. TicSync can get you tens of microseconds of precision in user space.