My understanding is the free draws count towards rare ninja but in no way at the 10th free draw does it guarantee anything whereas a 10 pull does. All that happens (assuming) is that there is an internal counter for rare ninja (60 SS) and free pulls do count toward it however once it hits the rare ninja draws required any free draw does not guarantee it can happen but chances are low, if you do get something on 10th free pull you should just consider yourself lucky.