Top window bar and bottom taskbar show up if the mouse is moved up or down far enough, and the latter still happens even when switched to tablet mode.

Here, you can see that Fullscreen is indeed on.

The top bar shows up if the mouse is moved up there.

As does the bottom bar.

Even in-game!

It's really quite frustrating, since I can easily accidentally click and open a new program or maybe worse, activate Cortana, and is literally the only thing keeping me from preferring Windows 10 version. Mojang...pls fix.