Remember that the RBI displays the position of the beacon relative to the viewpoint of the pilot, who naturally is looking along the direction the aircraft is travelling.
That is to say, if the RBI points to a bearing of 090, the beacon is not due East of the aircraft, it is in fact in the 3'o clock position relative to the direction one is pointing.
Imagine sitting in the cockpit of each of the aircraft and then viewing the RBI, and then where it would indicate the beacon would be...
Difficult to describe, bit I hope that get's the point accross...