I'm trying to confirm this is currently intended behaviour for List Views.
The List route /jira/software/c/projects/<ProjectId>/list explicitly filters out forge manifest provided custom (locked) fields of any type.
What confuses me is if you navigate to the corresponding filter in the filters view, you can add the custom locked field and it displays correctly there so it seems to be a product limitation that could be removed? Backlog views using list views display the field correctly, its specifically the List route / view.
Is there an open ticket for this?