I just purchased a rarely-used but poorly maintained early Japanese (1970s) Epiphone Riviera (a poor-man's 335). The pickups are installed reversed--the adjustable pole-piece screws are facing toward each other instead of pointing toward the bridge and neck, respectively. Furthermore, the pickup mounts appear to be reversed as well. The taller mounting frame was moved from the bridge position to the neck and visa versa. As a result, the neck PU is closer to the strings than original. Conversely, I suppose the bridge PU may be further from the strings than originally. With my Strat, if you run the pickups too high, the magnetic field interferes with the string vibration, stifling sustain and making it almost impossible to tune. The Epiphone's strings tune fine. Can you get too close with humbuckers?
All that said, it does sound great in all switch positions. Why was this done? Advantages? Disadvantages? Should I bother to reinstall them correctly? How would the sound differ?