TinyMce configuration not applied to block in page model

Description

Steps to reproduce

1. Install an empty Alloy site.
2. Set up a block and page:

public class ProductPage
{
   ...
   [Display(Name = "Test Block", Order = 45)]
    public virtual TeaserBlock TestBlock { get; set; }
}
public class TeaserBlock
{
   ...
   [CultureSpecific]
   [Display(
GroupName = SystemTabNames.Content,
Order = 5)]
  public virtual XhtmlString TestXhtmlString { get; set; }
}

3. Set up the TinyMce configuration:

config.Default()
.BlockFormats("Header1=h1")
.ContentCss("/Assets/css/editor.css");
 
config.For<TeaserBlock>(t => t.TestXhtmlString)
.BlockFormats("Header1=h1;Header2=h2")
.ContentCss("/Assets/css/editor.css");

4. Go to "Alloy Plan" page -> "Content" tab and observer the format option of TestXhtmlString.

Expected: Shows 2 formats: h1 and h2

Actual: Only shows 1 format, h1