This guy can do several per arm, on a ring:
https://www.youtube.com/watch?v=izSRjdYln8E
This skinny asshole (he appears to be a sort of performer?) can do multiple as pull-ups (not exactly, due to rotation around the arm) + weight on his strong side, as well as single finger variants:
https://www.youtube.com/watch?v=4HBQRYO105g
I would guess they are far more common in the small subset of people whose livelihood (and occasionally lives) might depend on them being able to haul themselves up with one arm: gymnasts, circus performers and other aerialists (I'm sure many trapeze artists can do them), and pro climbers.
I don't think anyone else really has all that much incentive to develop the skill.