I was trying to play on my singleplayer world with my friend over mobile data.

What I expected to happen was...:
When I joined a world with "Use Cellular Data" option enabled, the Multiplayer Game settings would be enabled and my friend would be able to join me.

What actually happened was...:
The Multiplayer Game settings were disabled automatically and my friend couldn't join me.

Steps to Reproduce:
1. Disable WiFi and enable Mobile Data.
2. Open Minecraft.
3. Enter a world with Multiplayer Game settings enabled.
4. Observe that they are disabled by default and that the world doesn't appear in the "Friends" tab.

The world is visible with Mobile Data on the device if the host is connected to WiFi. However, the device with Mobile Data enabled still fails to connect to the world.