I highly doubt there's any reliable signal in any of these points. Someone is only going to maintain a shell script if it has users or it continues to be useful

I highly doubt there's any reliable signal in any of these points. Someone is only going to maintain a shell script if it has users or it continues to be useful to them. But that fact is not significant regarding ability to deliver quality code. Not maintaining a project on github simply signals that the code isn't useful enough to anyone to maintain it. Many people have their favored hiring "hacks", and they almost never actually signal for the things they purport to. It's way too easy to fall into confirmation bias or overstate one's ability to judge others.