Dropped 3K - Batter runs to occupied 1B

[zoops]

I know this situation has been discussed here before, but in searching I didn't find a definite answer and a couple threads that went off the rails a bit.  Had this happen in a FED game a few days ago - batter swings at 3K in the dirt, ball bounces off the catcher and a couple feet toward the 1B dugout.  I signal and verbalize that the batter is out while the batter is beginning to run to 1B.  The runner at first attempts to advance and the catcher alertly takes a step or two to get the ball and then throws to 2B.  I do not think the retired batter interfered with the throw by his running up the line toward first, but what if he did?  It would appear that 8-4-2g in FED would call this INT, wondering more about OBR.

[noumpere]

If the retired B interferes, then the runner being played on is out. 

[zoops]

Thought there was an interp in OBR that if the runner continues running normally after being put out, he's not liable for INT.  Thought that might apply here.

[The Man in Blue]

The act of running on a perceived UK3 is not, in and of itself, interference (specifically: this is not considered an attempt to draw a play away from other runners) ... that does not mean he has immunity from committing interference in another manner or with another act (e.g., interfering with the throw on his way). 

I think that interp holds true for both Fed and OBR (and most other codes).