The short answer is yes, but you'll first need to create a metric on the Metric Definitions table. If you navigate to Metrics > Definitions and filter the Table column for *case, you'll see that there is already one metric for Assignment Group Duration for HR Case. You can use it as the basis for creating the one for assignee.
Here's a link to the Docs page for creating a metric: https://docs.servicenow.com/bundle/newyork-platform-administration/page/use/reporting/task/create-me...
Now, here's the tricky part...you'll report on the METRIC table. Not Metric Definition.
One other thing, because there's so much security around HR, you may also need to Allow a Restricted Caller access record the first time a Case is assigned. I'm guessing the call will already be allowed because of the existing metric, but check to be sure.
Hope that helps!
Lena
