[AndrewDucker]

You're not testing to tell MS that there's a bug. You're testing to make sure that your software doesn't break on the latest version of Windows.

[tacomagick]

You are actually testing for both, as an insider your feedback is asked every now and then, also you report issues you encounter willingly (Get Help metro app) or unwillingly (System Service/App stopped responding, collecting data and sending it to MS)