Sam,
Well... I normally try not to comment on the questions and explanations of other PMP Exam training companies. In this case, however, I have to agree with you that a BCR of 1.3 isn't all too bad. The real question here is, why do they think that it's "unfavorable". Maybe there is some other reasoning that we don't see.
So I have two recommendations for you:
First and foremost I'd say that you should simply shrug your shoulders and move on. It's probably not worth your time to get more into details here and you can invest your time more wisely in other studies.
Second, if you really want to know, then the best thing to do is to contact RMC directly and ask them for an explanation.