I repeated my experiment again, and now I note something interesting. The time delay I see seems to be matched by the "Time" counter in the top left. My host thinks the game is at 1:30 and my client thinks the game is at 1:21. Commands issues on the client (make your ark move) are immediately visible on the host at (say) 1:45, but the client then has to wait for its in-game clock to be 1:45 before the command is visible.
This starts from the very beginning of the game. When I hit "Start Game" on the host it immediately starts, but the client seems to have an 8 or 9 second delay before it gets the "game has started" message.
After some time I also saw messages like
10/20/2017 12:46:22 PM Waiting On Server, at frame 142
10/20/2017 12:46:22 PM Waiting On Server, at frame 142
10/20/2017 12:46:22 PM Waiting On Server, at frame 142 <=== this is the start of the game.
10/20/2017 12:50:31 PM Waiting On Server, at frame 2631
10/20/2017 12:50:31 PM Waiting On Server, at frame 2631
10/20/2017 12:50:32 PM Waiting On Server, at frame 2631
10/20/2017 12:50:32 PM Waiting On Server, at frame 2631 <=== this one now repeats and the game seems to be desync'ed, since the client clock has stopped advancing.
I did actually hit a crash (0019255) when repeating my experiment.