I had this exact sitch in a Jv tourney. Old BB guy is the coach. For what little talent he has he does a real good job. I called OBS. When he asked how the runner was OBS the best I could come up with is catcher impeded the progress of the runner. I wasn't real happy with my answer but I lived with it and I still am not real happy with my answer.
So people thread away so I can be a happy blue.
Also in our area this seems to becoming more of the norm, catcher setting up the line .