Filtering an XLV with a Managed Metadata Field in a Publishing Page Layout

Question

I have a custom Page Layout which inherits from Enterprise Wiki, with an additional column of type Managed Metadata.

In SharePoint Designer, I place this field as a control onto my customised page layout.

I add an XSLT List View (XLV) web part onto the page layout. This points at a Document Library that also has an additional Managed Metadata column.

I add a parameter to the XLV whose source is this field control (of type Managed Metadata).

I add a filter to the XLV such that my managed metadata column CONTAINS the parameter I defined above.

Now when I create a page from the page layout, the XLV never filters properly (it always returns no items).

However, if I set the Parameter in the XLV to get it's data from the QueryString, I can pass in something from there and it filters fine!

I have tried adding the Managed Metadata Field as a "FieldValue" control but this didn't have any effect.

(This might smell like a duplicate of Is there a way to filter a CQWP or DVWP using Metadata column values?, but I'm trying to filter via a FieldControl that is pointing to a Managed Metadata column).