Minecraft doesn't use borderless fullscreen

Minecraft 17w43b changelog states that:

LWJGL 3

… The biggest benefit you'll experience is that fullscreen mode now defaults to borderless windowed, so that snapping in and out of fullscreen mode is very quick!

However that is not true and Minecraft still uses regular fullscreen.

Steps to reproduce:

1. Open any application in a non-maxiazed window.

2. Open Minecraft in fullscreen mode (you can do so by either pressing F11 key or "Fullscreen" button in "Video Settings").

3. Use Alt+Tab to switch to that other app in a non-maxiazed window.

4. Notice that instead of that application appearing on top of the Minecraft window, the Minecraft window minimizes and only the the non-maximized window shows.

5. Repeat the same steps to reproduce above in any game or app, that supports borderless fullscreen. The application window shows on top of the game window.

Old description by @HalfOfAKebab:

"The biggest benefit you'll experience is that fullscreen mode now defaults to borderless windowed, so that snapping in and out of fullscreen mode is very quick!" https://minecraft.net/en-us/article/minecraft-snapshot-17w43a

The new borderless fullscreen feature is not actually borderless, it's just regular fullscreen. This results in delayed window switching (in fact, it's even slower than it was in 1.12.2), and the inability to screenshot with PrtSc.

In fullscreen mode, there is no way to take a screenshot without using the game's own screenshot functionality (F2). The PrtSc key simply copies a black image to the clipboard, rather than an image of what's shown in-game.