It is there and the examples work in singleplayer, but the mentioned multiplayer aspect of it (client-predicted, server-authoritative physics with rewind resimulation) is not working as advertised.
Even when using their example, after a short time all clients start to go out of sync and snap sporadically to their actual positions governed by the server. This happens increasingly more often the more clients join. I did the test with 12 players, where one is the listen server, on a packaged build.
PS. I’ve enabled the network prediction and its requirements and also did another separate test with a packaged build that had Iris enabled.