Batch update does not show values when using custom fields limited by event type

I've spent the day digging through the code and am not sure how to fix it (so I'm not assigning it to myself).

Here's how to re-produce (I've done this on the demo sandbox):

1. Create an event (just the first page - no other config necessary)
2. Create a custom data set of type participant restricted by event type using the same event type as the event you just created. Create just one field.
3. Create a profile with the field you just created.
4. Register a contact for the event, placing a value in the custom field you just created.
5. Do a participant search for all people assigned to the event you just created. Select the one returned record and choose Batch update.
6. Choose the profile you just created.
7. Result: the field you filled out for the contact is shown, but without a value.

I think the problem is in the CRM/Core/BAO/UFGroup.php file, in the setComponentDefaults method.

Around line 3165, we define two subTypes for events: role_id and event_id. That allows us to limit by participant role and event name, but not by event type.

Around line 3220 there is a call to:
CRM_Core_BAO_CustomGroup::getTree() which passes the $subType parameter but does not pass a $subName parameter.

It seems that we would need to pass both a $subName and $subType parameter for this to match properly.