It is not unknown for police to work up a 'Representative Sample" of cases for a longtime perp to plead guilty on, public knowledge as we have seen. I don't know if that then includes the entire case file of open cases getting presented to the judge or it is coded language that everyone understands, used to save court and police resources.
I believe there is the expectation that there is enough in the representative sample to get a good jail term by themselves. Perp expects a little leniency for having plead guilty but alternative is going down for the lot so not much discount.