Disgaea 2 Freichutz bow rank

Hey guys. I'm playing Disgaea 2 now and just unlocked the highest tier archers, namely Freischutz. However, their rank in bows is A, while the second highest tier archers have S, and so do the 3rd highest too. Is this merely a typo in the status window, or is it actually a bug that affects my skillups?

-e-
Figured it out.

I wouldn't be surprised if that was done on purpose though. Demons love to mess with you :p

I just wasn't aware that the skill scrolls didn't boost your skill rating by a set amount of points, it set it to A regardless of what your previous rating was.