In the preview 1.21.0.20, hardcore mode was added, which force disables cheats.

However, when you enable the experimental setting, it will also allow cheats.

Steps to reproduce

1. create a world.
2. enable hardcore mode and any experimental stuff (such as 1.21 update)
3. confirm to create the world.
4. enter a command such as "/kill @e", resulting in this world doesn't allow cheats.

What was expected: cheats aren't enabled, can get advancement or cheats are enabled, hardcore is disabled.

What happened: cheats aren't enabled, can't get advancements