This bug applies to the new experimental "Edit World" screen in the latest preview.

RECREATION:

• Create a new world in which you can't earn achievements (for example, set the game mode to creative mode)
• Exit the world, and then edit it
• Click on "You can't earn achievements. Read more.", it will say the following message:

• • You will not be able to earn achievements in this world with your current settings. If you would like to earn achievements, change these settings before creating your world: Set Game Mode to Survival."
• However, if you do change the game mode to survival it won't give you access to achievements, which is understandable as you already created the world, but the same message will still show up. (see image below)