I think they're making it short intentionally since the manga is nearing where the novels left off. Since if the manga finished off early it might lose interest, although they might make it long if we're at the climax of this chapter, that's just my speculations on this. I wish the publisher of Honobu Yonezawa would just let him published the next volume of Hyouka, since Honobu Yonezawa stated on his Twitter that he isn't the one who makes the decision to publish what he writes, although I might be wrong though