They have to call AFCI testers "indicators" because there is so much smoke and mirrors in AFCI technology they can't guarantee a "tester" will actually test one.
Yes I would agree, an inspection of an addition would require that you trip the AFCI and see which outlets go off.
I assume any receptacle in the new addition would have to be AFCI if you are 2008. I bet the best practice these days is to run a sub panel for any sizable addition since device type AFCIs have to be near the panel. You can't extend a circuit and drop a device type at the extension point. You could put the whole circuit you are extending on an AFCI, either by breaker if it is available or with a device type next to the existing panel.
