Description

Wide and full alignment options have disappeared in top level blocks in hybrid themes (themes that use theme.json but have not fully adopted block-based templates).

Step-by-step reproduction instructions

1. Install the Twenty Twenty-One theme.
2. Add a theme.json file with settings of your choice.
3. (Optional) Install the Gutenberg plugin version 15.0.1 or prior.
4. Observe that top level blocks can have their width options set as usual (for instance, Group blocks can be set to wide or full widths).
5. Install the Gutenberg plugin version 15.1.
6. Observe that width options in the editor have disappeared for top level blocks.

Screenshots, screen recording, code snippet

No response

Environment info

Fresh WordPress install with the Twenty Twenty-One theme.

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes