Yes. It is. On some occasions it's missing for more than ten seconds. It has never been this bad. This'll be fixed in the fourth beta though.
I agree that b3 has made it much worse.
My conclusion through debugging this is it's an issue with he status bar refreshing itself (in this case not). I suspect it's a trick to save battery life by reducing the amount of polling for status bar refreshes or something, or just a bug ...
Try this - put your phone into aeroplane mode.
Now the clock will stay hidden indefinitely - what triggers it to appear is something forcing the OS to refresh the status bar - eg, mobile signal or wifi indicators changing, or things like the Bluetooth logo appearing (hence why usually it would appear after 2-10 seconds for most people).
You can make the clock appear anytime by just forcing a status bar update. - toggle on Bluetooth or adjust your rotation lock to make either logo appear/disappear, and this explains why opening apps doesn't always make it come back (but would if it triggers say location icon to appear). Opening apps funnily enough makes the clock appear as the app opens, then disappear when you close the app.
I've reported this via the Feedback app, and I'm sure it'll get fixed.
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The new bug on 9.3 is much different. In beta 3 the time will only disappear when you unlock to the Home Screen and for anywhere between 2-10 seconds then it appears. Nothing is frozen. The time bug in 9.3 beta 3, you can force the time to appear sooner by opening an app. And the bug doesn't even appear if you unlock to inside an app. It's only when unlocking to the Home Screen.
This is actually incorrect. Opening apps does nothing, unless it triggers a refresh of the status bar. You can test this yourself as above - ideally with as few icons as possible on the status bar - eg, Aeroplane Mode, Rotation Lock, Battery indicator (no % indicator). Open an app that doesn't trigger location such as Settings, and the clock won't appear (but will flash up briefly and disappear when you return to the home screen).