If people are running low mileage there's a good chance that they have poor form and mechanics. After all, if you're doing <20 mpw you can just muscle through and not actually try being efficient. Plus they're not really training that much so when they inevitably go a few days without running they essentially lose most of their progress. So I can imagine they're way more at risk for stuff like shin splints.
I also wouldn't be surprised if they're including really minor stuff that well trained runners wouldn't count as an injury. If I wake up with aches and pains I wouldn't call it an injury, but I'm sure some people would because it still hurts to some degree.