What do you think undercover LE sounds like? "Good morning mr. kingpin sir, what grand criminal conspiracy are we going to undertake today?"

It's called "playing the part". The fact that no arrest has been made does make a compelling case that that entity was, at the very least, cooperating with law enforcement. They rounded up practically everyone else - even the witless compsci major who gave Ross a few coding tips back in the day. DPR's mentor not being arrested, despite his identity apparently being within reach of a determined government agency? That just doesn't make sense to me.