I agree with the OP. I can't see how this would result in getting a lighter sentence.

If the defendant disappeared, I don't see why the prosecutor would suddenly sweeten the pot with a great plea deal. And wouldn't the judge increase the sentence he was going to announce?

You shit-kicking, stinky, horse-manure-smelling motherfucker you! If you ever get out of line over there again, I'll smash your fucking head so hard you won't be able to get that cowboy hat on. You hear me? Fucking hick. -Nicky (Casino)