Earlier quoted context omitted.
Thanks for feedback. In principle it is a measure that says - this repo will handle your PR quickly, but the base chance of it getting merged is low. The result in this case is skewed by spam however. Until I find a way to filter the spam PRs from counting it will remain uneven for repos like this one.
That's exactly the problem. If you present a number but it's uneven for all kinds of reason it's a bad measure. And people will go around and unfairly point at projects being "bad for new contributors" with how you present it.
Spam filtering is at least something I should be able to tackle in a somewhat reliable way. I am worried about telling outsiders from insiders, there are many ways projects go about organizing their contributors! Some use GitHub organizations and give contributors membership (easy to tell apart) some others invite to collaborate via giving access rights (also easy) but some others do neither of those things.