IsReadOnly for PartEditBoxes in PropertyGrid

When the PropertyGrid has ReadOnly="True", the standard editors that use a TextBox set the IsReadOnly property of the TextBox, which is good because you can still select the text, scroll if its too long, etc.

But for editors the use a PartEditBox from the Editors.Interop.PropertyGrid assembly, it just sets IsEnabled="False" so this functionality isn't available. As PartEditBox now supports IsReadOnly, could this be changed?

I have tried with a custom property editor using an Int32EditBox and it works OK, but I'd rather not have to duplicate all the classes & templates from the interop assembly.