In existing worlds that already have external add-ons, achievements are disabled.

In the latest version of Bedrock Edition, using externally imported add-ons causes achievements to be disabled for the world, even if manifest.json contains "metadata": { "product_type": "addon" }.
This behavior is inconsistent with earlier versions, in which these add-ons did not disable achievements for the world.
This change can break game saves for players who rely on add-ons.

Steps to Reproduce:

1. Import the attached Test Add-on.mcpack into the game.

2. Open any world save with achievements enabled.

3. Activate Test Add-on in the Behavior Packs list.

Actual Result:
A notification appears indicating that achievements cannot be earned.

Expected Result:
No notification indicating that achievements cannot be earned should appear, consistent with older versions.