Metadatastore does not return editor settings for block properties

Description

1.Add code like this:

    [ContentType]
    public class MyPageType : PageData
    {
        public virtual MyBlock Block { get; set; }
    }
 
    [ContentType]
    public class MyBlock : BlockData
    {
        public virtual string MyString { get; set; }
    }
 
    [EditorDescriptorRegistration(TargetType=typeof(MyBlock))]
    public class MyBlockEditorDescriptor : EditorDescriptor
    {
        public override void ModifyMetadata(ExtendedMetadata metadata, IEnumerable<Attribute> attributes)
        {
            base.ModifyMetadata(metadata, attributes);
            metadata.EditorConfiguration["baseClass"] = "my-css-class";
        }
    }

2. Create a page of the new type MyPageType.

3.Inspect the html element for the block when editing the page.

Expected: The element has the custom css class "my-css-class."
Actual: No custom css class. The standard "dijitLayoutContainer" class is used instead.