Autostart on NFC tag touch does not work on Symbian

Autostarting an app on touching an NDEF tag with a custom RTD record through the method documented in Qt Mobility does not work on Symbian.
Attached a simple example app to reproduce. Used the Nfc Interactor example to create the custom tag (https://projects.developer.nokia.com/nfcinteractor).

Created the XML file for Symbian according to the documentation at:
http://doc.qt.nokia.com/qtmobility/qnearfieldmanager.html#automatically-launching-ndef-message-handlers
Specified the following custom RTD (following the standards of the NFC Forum External Type): "urn:nfc:ext:nokia.com:corkboards"

In the app, I register the NDEF message handler using as documented:
"nfcManager->registerNdefMessageHandler(this, SLOT(targetDetected(QNdefMessage,QNearFieldTarget*)));"

But still - touching the tag when the app is not running makes the phone emit the default message: "Unable to read tag. Format not supported."
Even touching the tag while the app is running also leaves the OS to handle the tag and doesn't forward it to the already running application.

Registering for the same custom RTD using a native Symbian ECOM plug-in (based on https://projects.developer.nokia.com/nfccontenthandlerplugin ) works fine and the handler is executed on touching the tag. So the issue is definitely not with the tag, but with the Qt Mobility tag handling implementation.