No matter at this point. It is part of the plea agreement. Make him take the ploygraph, and if he refuses then cancel the plea deal and re-open the case against him for treason.
Polygraphs are pseudo-scientific trash, with no real validity. It's a sign of their incompetence that so many police agencies put any faith in them. They are not accepted as evidence in court. Notice that Burglar himself agreed to take one. It's just possible that the Injustice Dept. doesn't want to bother because they think he might pass. However, it's more likely that that they want to shove the matter under the rug. Scumbags all around. The Washington insiders protecting themselves from us.
I sure hope this works out as you propose but doubt it will as he's gotten a relative free ride versus the rope for treason.