C++ types exposed by QmlDesigner::IWidgetPlugin are not listed in Library view in QML Designer

Hello,

I have created my own custom QML types library using QQmlExtensionPlugin.
I have successfully imported it into my QML project. Everything works fine, I can edit my types in QML editor and run my project without any problems. My plugin contains both C++ types and one type defined in .qml file. My qmldir therefore looks like this:

module VideoPlugin
plugin VideoPlugin
TestModule 1.0 test.qml

Now I also created QML designer plugin using QmlDesigner::IWidgetPlugin. My .metainfo file looks like this:

MetaInfo {

    Type {
        name: "VideoPlugin.VideoSurface"
        icon: ":/QFlow/images/player.png"

        ItemLibraryEntry {
            name: "VideoSurface"
            category: "Video Modules"
            libraryIcon: ":/QFlow/images/player.png"
            version: "1.0"
            requiredImport: "VideoPlugin"
        }
    }
    Type {
        name: "VideoPlugin.Dilate"
        icon: ":/QFlow/images/player.png"

        ItemLibraryEntry {
            name: "Dilate"
            category: "Video Modules"
            libraryIcon: ":/QFlow/images/player.png"
            version: "1.0"
            requiredImport: "VideoPlugin"

            Property { name: "iterations"; type: "int"; value: "1"; }
        }
    }
    Type {
        name: "VideoPlugin.TestModule"
        icon: ":/QFlow/images/player.png"

        ItemLibraryEntry {
            name: "TestModule"
            category: "Video Modules"
            libraryIcon: ":/QFlow/images/random.png"
            version: "1.0"
            requiredImport: "VideoPlugin"
            Property { name: "test"; type: "int"; value: "1"; }
        }
    }
}

I have put plugin .so file into qtcreator/lib/qtcreator/qmldesigner.
Designer successfully loads the plugin and calls metaInfo() method and retrives the metainfo.

When I open the QML designer, I can see that there is a new library in Library window. However, the library contains ONLY THE TYPE DEFINED IN .QML FILE AND NOT MY C++ TYPES. The funny thing is that I can nicely edit my C++ types, edit properties, they work fine in Form Editor and also an icon is assigned to instances of those types. So the QML designer loads the plugin, gets metainfo, assigns icons but it doesn't list my C++ types in Library window.

Am I missing something or is it a bug?
I considered to create a bug report because I don't see any reason for this behavior.

I also attached a screenshot where you can see QML editor where a pure qml type is listed in library, the C++ type is selected in Form editor, it has icon but is not listed in Library view.

Cheers.

Michal