Application UI extensions contextIdentifier behaviour

Hi,
I'm trying to set application UI extensions using PATCH /api/http/applications/ui-extensions.

The goal is to have a global issue menu item and a menu item specific to a project.

I'm making two requests with the following payload and I was expecting to have two buttons on project 1YNPl907KYh7 and a single button for the other projects. Is there anything wrong with this or am I misunderstanding the goal of the contextIdentifier?

{
    "contextIdentifier": "project:id:1YNPl907KYh7",
    "extensions": [{
        "className": "IssueMenuItemUiExtensionIn",
        "displayName": "project context",
        "menuItemUniqueCode": "project-context",
        "visibilityFilters": []
    }]
}

{
    "contextIdentifier": "global",
    "extensions": [{
        "className": "IssueMenuItemUiExtensionIn",
        "displayName": "global context",
        "menuItemUniqueCode": "global-context",
        "visibilityFilters": []
    }]
}

Thanks