This came up earlier this year and honestly I cannot remember the exact answer... it came up again on the FP discussion section in a discussion about who covers 3rd when F5 is fielding a sacrifice bunt...
so, what I recall is that F2 does not have to wait for BR to clear. Especially with a RH bunter, and a bunt placed on the right half of the infield, a fast catcher could jump toward the bunted ball and, if she doesn't "wait for BR to clear", will likely collide with BR since their paths cross each other. Many BRs wait about a second after contact on a sac bunt to make sure the bunt gets down cleanly. If F2 were to wait until after this BR in this situation started running toward 1st and cleared F2's path, F2 is wasting about 1.5 seconds in time.
So I ask again, if F2 and BR collide (outside the batter's box), and F2 is on a direct path to field a bunted ball, what is the call? a) no call, play on. b) obstruction on F2, c) interference on BR. d) something else?
Oh, I assume BR is not still in the batter's box... but has just exited the batter's box and the collision occurs just in front of home plate.