My recent question about an APC UPS was closed as off-topic ("This question is not about computer hardware or software, within the scope defined in the help center.") I flagged another UPS-related question as off-topic since it was a very similar to mine. The flag was declined. How can I decide which UPS-related questions are on-topic here?

If I'm right both questions could belong to the...

electronic devices, media players, cell phones or smart phones, except insofar as they interface with your computer,

...off-topic reason.