Users who didn't made a report in the last 30 days, normally couldn't find anything in their history.
If you mean that you have for example less than 10 reports and you couldn't see how many are good/bad/unhandled then probably you are right about the minimum requirement (even if i don't understand the reason behind it)
It was a long time ago now but I remember when I first started reporting that my accuracy stayed on 0% for a while. I guess it might be a minimum sample size required to make a percentage relevant.