Where is this in the law? This was a serious point of contention and is certain to be appealed if a conviction is based on this. It is also not what some are making it seem like. It does not mean that they can different between charges but rather what the underlying crime he was covering up was.
They must be unanimously on two things.
1 - he falsified business records
2 - he did so intending to commit a separate crime
They don't need to be unanimously on the separate crime. That is the Judges understanding of the law.
ETA: This doesn't seem uncommon. A prosecutor gave an example of someone being guilty of murder even if the some of the jury felt the murder weapon was a bat and others thought it was a pipe.