IT IS 100% up to the judge---I am fairly sure that the plea agreement was non-binding. Further, he who speaks first about the other conspirators usually gets the best deal. From reading the transcripts I would guess this fella spoke the most and quickest regarding the other defendants. Therefore, the prosecutors will make a recommendation to the judge which will be based on how much he really helped them obtain the convictions.
I can say with certainty there were several of the charged that never cooperated and received the most time. There is a rumor ( with some facts) that this investigation started in 2015 at Chester ----not sure of the facts but there is reason to believe this is true.
Further, usually the last person to get sentenced in a conspiracy is the informant because the prosecutors want to evaluate his cooperation level and how he followed zthe terms of the plea.
The sentencing is usually schedule 30 days out from the last sentencing in case there is a appeal by one of the sentenced. Most plea deals do not permit appeals but generally the judge will allow an appeal in order to stop expensive litigation down the road.
This case is terrible proof on how this industry has fallen---if these folks get away with killing horses ----then there should be no racing anywhere in the world. If all is true ---then these fellas are lucky with the sentences that they received.