It's interesting that Meta is doing such serious low level R&D like this, but it's funny because they can't even keep their notifications in sync with their web site. I get a notification (from the mobile app, I think) that Joe has a birthday today, I go to the web page to wish them a happy birthday, and despite reloading, the web site still shows the birthdays from the previous day. Then I have to dig around more to find Joe's page to post a HBD.
So as user, this level of time synchronization seems to be many orders of magnitude of over kill. I'm sure at some level it is actually important, but it seems like the database sync or whatever is going on with notifications is woefully lagging.