Well, if that were true - that by simply being on the bike an RR is now required, then you'd have to say that a 2nd person riding on that bike would get the RR benefits of the first person, or both, or something.
In my own game I'd rule that the bike could be affected - but the driver would be able to react with piloting skill to try and maintain control.
Still, would like to hear what the designer had in mind for this situation.