This might have been an oversight and might have been implemented before the XboxOne app achievement system. Kinect PlayFit is an Xbox 360 App and it actually has achievements! So shouldn't this app count towards the Apptastic badges? The description doesn't say Xbox One only.
Unlock 10 app achievements on your gamertag.
Please let old threads die and do not reply to them unless you feel you have something new and valuable to contribute that absolutely must be added to make the discussion complete.
Otherwise, please post a new thread in this forum instead.