Changing the game mode setting in the Open to LAN menu immediately changes all guests' game mode

Due to the changes made recently, gamemode and defaultgamemode have become extremely inconsistent, inconvenient and incomprehensible. I am going to explain all the different scenarios that cause unexpected behavior in a series of tickets after I lay down the expected behavior. These were all covered in a single ticket by another user, which was resolved because it was invalid due to multiple bugs in one ticket.

Terminology

• World visibility state

  • Singleplayer: A world that is created through singleplayer world creation, is NOT open to LAN only housing a single player.

  • Open to LAN: A world that is created through singleplayer world creation, but is opened to LAN. It houses 1 or more players.

  • Multiplayer: A world that is created through dedicated server multiplayer world creation. It houses 0 or more players.

• Gamemode state

  • (Player) Gamemode: The gamemode of an individual player.

  • Default Gamemode: the default gamemode of the world which is traditionally modified with /defaultgamemode and shows up on the level select screen in singleplayer. (or in server.properties > gamemode=<GAMEMODE> for servers)

  • LAN Gamemode: the temporary default gamemode which applies only in Open to LAN worlds to other players.

  • Forced Gamemode: the gamemode to switch players to upon joining. Found in server.properties force-gamemode=<bool>

Expected

• Either changing the gamemode for other players in Open to LAN settings should only change newly joining players' gamemodes, or the fact that it changes all current guests' game mode as well should be made more clear.

Actual

• The host changes the gamemode for other players in Open to LAN settings: this changes everyone’s gamemode except the host

Please check the attached video. It explains many of the issues found in the post I am copying from (but not all), as it visually shows many of these scenarios. Minecraft Game Modes Are More Complex Than Quantum Mechanics...