Trying to access the nether in Debug World has weird effects

After I opened a world in debug mode, I purposely didn't go on /gamemode 3.

I saw a portal block, and entered it to see if the Nether is generated similiarly.

It'll freeze the game for 20 seconds, then summon you in an oddly generated, chunky world.

If you will move, the game will crash.

Crash report attached.