Minecraft prevents users from disabling data packs which enable feature flags. I would expect this to only be the case when disabling a certain data pack would actually lead to a feature flag getting disabled as well. This is not the case when two data packs enable a feature flag, but the user is still prevented from disabling one of the data packs.

How to reproduce

1. Create a new world and install the attached data pack.
2. After loading in the world, verify that the update_1_21 feature flag is enabled (for example by finding copper bulbs in the creative inventory)
3. Verify that this data pack is enabled but the "update_1_21 (feature)" data pack is not.

   /datapack list
   

4. Enable this builtin data pack

   /datapack enable update_1_21
   

5. Try to disable this data pack again. This should be no problem because the update_1_21 will still be enabled by the custom data pack that was enabled from the start.

   /datapack disable update_1_21
   

6. You get the error "Pack 'update_1_21' cannot be disabled, since it is part of an enabled flag!"