Can of corn on this one for me, since I've got that T-shirt. I don't have the reference, but the FED interp is essentially this: It's up to the defense to know what is going on, and the situation you've described is NOT interference on the offense.
We have a local HS team that routinely does this under the guise of "hustle" - we're convinced as umpires here that they do it to try to draw a throw, but there is nothing illegal about the B/R running, even passing another runner. I issued the coach a friendly warning (it was a preseason tournament game - a glorified scrimmage) when I first saw them do it about three years ago, but after looking it up afterwards, found that it was not illegal.
It certainly doesn't look good, and usually looks intentional. Intent, as I recall, does not matter, and is especially hard to prove in this case.