As to how do they tell if its a stranger renter or a friend - that's easy. They probably already subscribe to a fraud service that will tell you if two people are associated. (This is how
Best Buy avoids shipping a TV to a scammer who has your credit card - they know what addresses and people you are associated with and if the TV isn't going to you at your home, they check. And they discover its your stepson in college with a different last name and ship it without a phone call). That's been happening for at least fifteen years. As long as you are associated (graduated from same college in the same year, worked at the same place), they will figure its plausible. It even gives you a weighting on how associated these people are - someone I'm working with now, likely. Someone who graduated from a huge public university the same year I did forty years ago who isn't even on any of my social media lists - not high.