No, there is nothing to report at this time.
It’s on the long list of features but it isn’t a simple thing to implement given the additional interface changes required to display custom metadata.
but the DTTG ‘Comments’ metadata field doesn’t seem to sync back to DT3. Or have I missed something?
I’d guess you’re looking in the wrong place. You need to look at the Finder Comments in the Annotations & Reminders inspector not the Info > Properties inspector.